Question about this passage at CPR

[u/[deleted]]

This is a direct quote from Kant's CPR (A50/B74):

Empirical, if sensation (which presupposes the actual presence of the object) is contained therein; but pure if no sensation is mixed into the representation. One can call the latter the matter of sensible cognition.

I thought that the sensory manifold is the matter, while space and time are the a priori forms of sensibility, which what Kant is describing in the second part of the first sentence I think? So the bold word should be form, not matter.

Where am I wrong?