Identify a card please

[Trees]

I have  a small card which belonged to a driver in the Army Service Corps during WW1 please can any one explain what it is and how we can interprate the information.I have only indicated areas where information has been added it is very faint and grubby. His medal card has him as a private and not Sargeant 

Unit Register Card      A.G.Z.500 FRANCE
RA   86 M T
1.Dispersal Area in UK to which proceeding   IVB
2.Industrial Group as shown on AFZ8 26/43
3 Trade or profession Smith's striker


6 Single

8 Length of service in years 15-3-18
9 Service in the Field in years in the present war 17-7-16
10 Service category I  t or x] A
11 Medical Category B1
12 Specialist Qualifications 1/c Driver
13 year of birth 1898
14 Corps RA 86  7UT
15 unit 6 th aux (9) co
16 M/372582 Sgt seems added later over private
Jones W J

On reverse Movements From Concentration Camp to Embarkation Camp
list of numbers at bottom under
(8 17 93) W839- RP4179 100,000  5/19  HWV(P67)
18 15  3 18 27 ?
19 -  -  - -   22
20 200---   23


Grateful for any help
Trees