Rifles up to 11,XXX is a generalization. In my references I see carbines and rifles up to 1,7XX, then mostly rifles up to 11,000, but with mixed rifles and carbines in the 4,800-7,XXX range. In the low 12,XXXs a mix of carbines and rifles, then most or all carbines until the 21,XXXs, then mostly rifles in 22,XXXs and into 23,XXXs before back to almost exclusively carbines to the end of the 1860 Model production. The carbines below 1,7XX don't seem to fit the accepted narrative of Spencer production--perhaps those numbers were initially reserved and then used later.
--DJ