Your b-spec level goes up as you run and win races in the b-spec side of GT5.
When you are grinding, your drivers may be of a higher level than your overall level. Just run a few of the b-spec races, and that will level you up quickly...
Ive left mine on all last night and i already had a level 30 driver but now the others which were all zero are now on mid 20's and got about 1.5 mill out of it.
I started it off again on remote races this morning and just checked at work and its still showing they are running so when i get home about 6pm tonight hopefully they will have all gone up to mid 30's
I mainly want to get my B Spec to level 40 and get all the races out the way and then i can concertrate on going back to doing the A spec which is on level 30 already.