These are latency timings. In other words, how many delay cycles before a certain function occurs in memory.

The first number is always the CAS latency. The 1t on the end is almost always the command rate. The other numbers can vary for what they are, depending on who posts them, but usually the second number is the RAS to CAS dealy (Trcp) and the third is RAS latency. I can't remember right now what that fourth number is.

If you want some really good information on BIOS settings, including the memory timing information, check out this site.

http://www.rojakpot.com/default.aspx?location=1

Click the link on the left side of the page for the BIOS optimization guide, then start scrolling.