The designer has written some text on a drawing of a costume for a play:

"Соловей"
Придворныя дамы
числомъ 6
одинакихъ
такихъ 2

My question is: why the use of числом in the instrumental? Can you give some other examples of this?
I understand it to mean that there are six costumes for Court Ladies, and that two are identical to the one in the drawing. There may be other drawings of the rest. Thank you.

(pre-Revolutionary spelling)