it's not unusual for a soldier to have two numbers in the same regiment if he was serving in a territorial battalion, as they were re-numbered with six figure numbers in 1917.
if he would have moved regiments then he would have had a new number but his new regiment would have been on the card as well and an indication as to which regiment issued his medals.
what is unusual on his card is that there is a second number but it's too low to be a territorial 1917 number ( these started at 200000)
going back to my original musing i thought he went to france around the time the new armies (K1,2,3) went over. making him a 1914/15 volunteer. doing a quick analysis of the numbers in the 25*** range, they were given out to the service battalions raised in 1914 (generally 10th to 15th) which strengthens my conclusions
These battalions had been disbanded by 1920 and yet James was still stating his occupation as soldier and giving service number on his MC , i am wondering if he actually stayed on in the army and was in the 1st battn by that time ( the 1st battn being a regular army unit)
if he did stay on beyond 1923 then his service records will be with the MOD in Glasgow. The other way of ascertaining the battalion ( assuming his records don't appear on ancestry) would be to get someone to look at the medal rolls at Kew and the info from them