Firstly Vernon, F & T stands for Fireman & Trimmer not Fitter and Turner.
Where it shows birth year and it has 31 there it means his age i.e. 31.
So you have the wrong man which has been confirmed by Sid stating his discharge number 555686 which is the same one on the cards I have.
For Sid,
The number you refer to is his RS2 number which is his identity number which is different from his discharge number.
What records do you have that show the gap in service between 1939 - 1944?
Regards
Hugh