The reps go up by 5 every level.
The EXPERIENCE of skill points you get FROM each rep goes up too, but, is ALSO related to your RIG, and its MODS, and to ALL your stats.
I get over a thousand points per train session (Say where you'd use 15 glitter to refresh...)
The training varies though, just like some of your hits do 100 damage, and some do 50 or 200 or whatever...the training varies the same way...
So you might do one set and get X points, do another and get X-25%, or, X+25%, etc.
This gets magnified if you use the Power Trainer...as that variance is proportionally magnified.
The game uses RANGES for all stats. NOTHING is exact.
That means you might JUST beat a guy one time, and he might JUST beat you the next, etc.
That's why the races are so crazy...I might win by 0 lengths, 6 lengths or 12 lengths, all in a row against the same competitor.
So, when training, it all averages out eventually.