202761 is the number he first went overseas with. It doesn't tell you when he enlisted, but shows that he didn't go overseas before the Territorial re-numbering in early 1917. It is a 4th Battalion number.
The Labour Corps number 580402 falls within the batch issued May to September 1918. (Courtesy of "No Labour, No Battle")
I don't have access to Ancestry, so can't check to see if there are any clues on the card (such as discharged with SWB etc).