I'm trying to save a curve from my 370A to it's floppy but I'm getting an error message - what's going on?

I'm trying to save a curve from my 370A to it's floppy but I'm getting an error message - what's going on?

The floppy drives in 370A/371A support 720K diskettes only. To use 1.44M media, tape over the empty hole in the upper left corner of the diskette (i.e. the one opposite the write protect switch). The 370B and 371B use standard 1.44M drives.