Hi there,
I can't tell you exactly what code 24 means to Gigabyte but, as an end user, I know that it means the system is working correctly, hardware has passed all checks and that Windows OS is loaded and running.
Some codes that show on the LCD are, according to the manual, system reserved and trying to discover what they refer to is a bit like trying to find the pot of gold at the end of the rainbow.
Basically, if your LED is showing code 24 then there are no problems.
Hope this helps.