The A position is forward. This ratio is 2.72:1
The B position is reverse. This ratio is 2.15:1
ZF publish full information in their literature and the shop that is advising you has not taken into account the differant shock factor that must be applied to get reliable service
Position A is normally ahead.
These are the maximum ratings:
R: 2.045 38 hp @ 3000 3 cyl shock factor adjustment 38hp/1.15 = 33 hp
R: 2.722 27 hp @ 3000 3 cyl shock factor adjustment 27hp/1.15 = 23.5 hp
The intermediate gear will not survive constant power transfer. When used in the B position, the intermediate gear will be used and the bearing that this rides on will not work for long.