control in modern ui file

what is this control in dialog 103 for:

CONTROL "", 1008, BUTTON, BS_AUTOCHECKBOX | WS_CHILD | WS_TABSTOP, 180, 110, 118, 10

?

i think, dialog 103 is the directory page, isn't it?
while i want to add another control to it, i just wanted to know, which controls do what. 🙂

another question:
what stands this option for in the ChangeUI command?

IDD_VERIFY

The checkbox is for installers with log enabled. When you hold shift when moving to the directory page, it will show.

IDD_VERIFY is the little window that shows when the installer does the CRC check.