well according to the post i tried the following:
//echo -a $calc(10000000000000000000000 + 0)
it returns 10000000000000000000000
which is perfectly fine.
but when i try to add another 0 behind
//echo -a $calc(100000000000000000000000 + 0)
it returns 99999999999999992000000
seems like the problems only affect with int numbers bigger than 24char