What are the numbers on the shirts of cricketers mean?

The numbers on the England Cricket shirts below the 3 lions relate to their cap number, These differ depending on if its Test Matches or ODI matches

Andrew Struass is 624 for Test Matches and 180 for ODI and 9 for T20

http://www.ecb.co.uk/news/england/england-player-numbers,321,BP.html