why substract 0xe7 from leaked libc_start_main address in everybodys_got_something_to_hide?

[ackbar03]

Hi,

This is prob a noob question but for the hard address leak in everybodys_got_something_to_hide, why do we need to subtract a offset from the leaked lib_c_main address?

https://github.com/shellphish/ictf-2020-challs-public/blob/1e0b7c1fde9b5c8ff2d3e1ca428c4396d63e046e/everybodys_got_something_to_hide/scripts/exploit#L106

libc_base = libc_start_main - libc.symbols['__libc_start_main'] - 0xe7

I understand that the libc_start_main is pushed onto the stack at somepoint during runtime, but why is a offset necessary?

Thanks!