format disk

Hi,...
have some problems during farmatting.

Loaded the workbench in df0
and a "blank disk" created by winuae in df1.

Tried formatting df1 ,...it startet but a popup-Dialog
informs me "not a dos disk", after that "verifying-formatting"-Dialog.

What does this mean.
(can´t remember ,it´s many years ago I owned an amiga)

p.s. Needed the disk for saving.