3-4-4-5 are the RAM timing values for CAS latency, RAS# to CAS#, RAS# Precharge, and Tras (Just like the values shown for your existing memory under the 'Timings Table' if you read each column from top to bottom for each of the three bus speeds.
To be sure of getting an identical module your best option is to stick with that brand and do a search online for that manufacturer/part number if it's still available, as shown in your screenshot.
If all you want is compatible RAM with a 'money back guarantee' if it doesn't work, go to Crucial and use their 'Scan My System' tool.http://www.crucial.com/uk/
The timings values for a module do not have to be identical to your existing RAM in order for them to work together in your system. Only serious overclockers and 'geeks' bother with that side of it. The rest of us don't give a hoot about timings just so long as it works.
Edited by pip22, 15 August 2007 - 08:15 AM.