What does "se.infra@SEP-138#1" mean on kernel version? I have broken my mobile, so I want to download the original version back.

The original version is:


Android version: 4.1.2
Kernel version: 3.0.31-638230 se.infra@SEP138#1


On kernel version, what does it mean by se.infra@SEP138#1 and how to check the correct kernel version before downloading the Android image?
This is the name of the user and computer that was used to build the kernel. "se.infra" isn't a username belonging to a real person, but an account used by the build infrastructure at Samsung. It's not relevant at all.

The thing you need to match is the Build number, shown just beneath the kernel version in the About device page of the device settings. It looks something like JSS15J.I9300XXUGNG3: everything after the "." is actually the build number for the baseband (modem firmware) that goes with the ROM. The first half of the build number is listed with each ROM on sites like sammobile.com that offer original Samsung ROMs for download.