A bit few for 4 bns isn't or do they plan to give pre series vehicles to the armour schools and driving schools?
They're probably meant for experimental exploitation.
As for numbers, a tank btln in a Tank bde is still 31 tanks, in Motor-Rifles they were increased to 41 tanks. Motor-rifles btlns are 3 line companies, plus an HQ element. Something like 32-35 armored transports. 100 would equal ~3 btlns but iirc the news were't "exactly 100 ordered" they were "around a hundred". Since it makes little sense to order 2 btlns of one and 1 btln of the other, I suspect the real numbers are around ~120-130, and it's 4 btlns, 2 of each. Normally one btln set is enough for experimental exploitation (state trials have already begun with the LRIP vehicles that were delivered prior to this contract), so it's also possible that the order includes two btlns (41 tanks, 35 IFVs), plus an ARV company. Honestly though I'm not sure. It's even possible that they've ordered 3 tank 1 IFV or the reverse, and are going to re-equip an entire brigade at once, and run experimental exploitation that way. I think we will have to wait and see, and we might not even get to see.
Case in point, the 2S35 Coalition-SV howitzer is currently undergoing state trials and experimental exploitation, one near Yekaterinburg, and one near Moscow, but which is which, and how many total units there are is completely unclear. The only way we know is because parade boxes showed up on May 9th of this year in both towns.