The main thing to remember of Indian units, North and South, was they tended to shift on numbers constantly.
@ucvrelics link and 300 number sounds about right.
Indian troops in the I.T. tended to desert more than any other type of unit. If they got defeated, they'd switch sides, if they won a battle, they'd go home, and if there was nothing going on but marching and riding, they'd just go home on that to.
Stand Watie's troops did get up to the 1,000 range for the 2nd Battle of Cabin Creek, and the Sinking of the
J.R. Williams, Oklahoma's only naval battle, but after both battles the troops would loot what they could and go home. With the
J.R. Williams, that victory disintegrated Watie's force. The memoirs of one mix-blood captain lay out how his company was to be the rear guard, and he ended up doing the job all by himself cause his men looted the ship, and took off.
Most reliable thing with Indian troops you could count on was that they would be unreliable.