I think the bottom manuscript cancel is "cancel your stamps" -- maybe an admonishment from someone at the bank to the check writer, Elizabeth Strong, for not cancelling the stamp. Ms. Strong doesn't seem to be to familiar with the process, note that she wrote the denomination of the check on the check number line.
Curious and creative doodle. Since it was done in a completely different ink from the cancel, who knows when it was done, i.e., contemporary or by a stamp collector after the fact. It would be interesting to see whether the heart fluoresces.