Uniswap v3 unclaimed rewards calculation is off

Question

I'm creating a statistics app for tracking my positions on uniswap.

As you can see below I have 0.019 unclaimed ETH rewards. However, when I try to reproduce this in my statistics app, I get 0.016 unclaimed ETH rewards. When running the numbers for the USDT token it is also off by about 10USDT. I will walk you trough how I've done this:

I get my active positions using a graphql query from the Uniswap API, you can run the query at https://thegraph.com/explorer/subgraph/uniswap/uniswap-v3:

{
  positions(where: { owner: "0x44A2432332ca9166EC606501DA8067fC3C3c9058", liquidity_gt: 0}) {
    liquidity
    feeGrowthInside0LastX128
    feeGrowthInside1LastX128
    token0 {
      decimals
      derivedETH
    }
    token1
    {
      decimals
      derivedETH
    }
    tickUpper {
      tickIdx
      feeGrowthOutside0X128
      feeGrowthOutside1X128
    }
    tickLower {
      tickIdx
      feeGrowthOutside0X128
      feeGrowthOutside1X128
    }
    pool {
      tick
      feeGrowthGlobal0X128
      feeGrowthGlobal1X128,
      totalValueLockedUSD
    }
  }
}

Using the information I found at https://blog.uniswap.org/uniswap-v3-math-primer-2#calculating-uncollected-fees-in-a-position I created the following functions (C#) to calculate the rewards.

var value0 = CalculateReward(
    BigRational.Parse(position.Liquidity),
    BigRational.Parse(position.Pool.FeeGrowthGlobal0X128),
    BigRational.Parse(position.TickUpper.FeeGrowthOutside0X128),
    BigRational.Parse(position.TickLower.FeeGrowthOutside0X128),
    BigRational.Parse(position.FeeGrowthInside0LastX128), 
    position.TickUpper.TickIdx, 
    position.TickLower.TickIdx, 
    position.Pool.Tick);
value0 = value0 / BigRational.Pow(10, position.Token0.Decimals);

private BigRational CalculateReward(
    BigRational liquidity,
    BigRational feeGrowthGlobal,
    BigRational feeGrowthOutsideUpperTick,
    BigRational feeGrowthOutsideLowerTick,
    BigRational feeGrowthInside,
    int tickUpper,
    int tickLower,
    int tick)
{
    var feeGrowthInsideCurrent = CalculateCurrentFeeGrowthInside(
        feeGrowthGlobal,
        feeGrowthOutsideUpperTick,
        feeGrowthOutsideLowerTick,
        tickUpper,
        tickLower,
        tick);
    return liquidity * (feeGrowthInsideCurrent - feeGrowthInside) / BigRational.Pow(2, 128);
}

private BigRational CalculateCurrentFeeGrowthInside(
    BigRational feeGrowthGlobal,
    BigRational feeGrowthOutsideUpperTick,
    BigRational feeGrowthOutsideLowerTick,
    int tickUpper,
    int tickLower,
    int tick)
{
    var feesBelowLowerTick = CalculateFeesBelowLowerTick(feeGrowthGlobal, feeGrowthOutsideLowerTick, tickLower, tick);
    var feesBelowUpperTick = CalculateFeesBelowUpperTick(feeGrowthGlobal, feeGrowthOutsideUpperTick, tickUpper, tick);
    return feeGrowthGlobal - feesBelowLowerTick - feesBelowUpperTick;
}

private BigRational CalculateFeesBelowLowerTick(
    BigRational feeGrowthGlobal,
    BigRational feeGrowthOutsideLowerTick,
    int tickLower,
    int tick)
{
    if (tick >= tickLower)
    {
        return feeGrowthOutsideLowerTick;
    }
    else
    {
        return feeGrowthGlobal - feeGrowthOutsideLowerTick;
    }
}

private BigRational CalculateFeesBelowUpperTick(
    BigRational feeGrowthGlobal,
    BigRational feeGrowthOutsideUpperTick,
    int tickUpper,
    int tick)
{
    if (tick >= tickUpper)
    {
        return feeGrowthGlobal - feeGrowthOutsideUpperTick;
    }
    else
    {
        return feeGrowthOutsideUpperTick;
    }
}

For example, if I run the following numbers (which I got from running the above graphql query) through the calculations, I get 0.016 instead of 0.019. What am I doing wrong?

var value0 = CalculateReward(
    BigRational.Parse("1367429764868973"),
    BigRational.Parse("356531773596110297175139730895619992793974"),
    BigRational.Parse("0"),
    BigRational.Parse("349599952281522978521834276098134191845749"),
    BigRational.Parse("2736330194804551556695334267654167873990"), 
    -196915, 
    -199341, 
    -198304);
value0 = value0 / BigRational.Pow(10, 18);

I also tried communicating with the smart contracts directly, with the same result.