Soldity can't handle floating point numbers so it must store decimals in integer form.
The 1e<n>
notation basically means "1 followed by n number of zeros". So 1e2 is equal to 100 and 1e4 is equal to 10000, and so on.
The expression 444 * 1e6 * 1e18
then means:
444
1e6
= 1000000
(6 zeros)
1e18
= 1000000000000000000
(18 zeros)
so TOKEN_LIMIT = 444 × 1000000 × 1000000000000000000
There are 444,000,000
total tokens (444 × 1e6), but taking account decimal places (the SOMN token supports up to 18 decimal places) it then becomes (444,000,000 × 1e18).
TLDR; 1eN is exponential notation, to better represent the number of zeros. Solidity only supports fixed-point numbers.