Suckers are new little plants, complete with a tiny crown, developing in between the leaves at the stem or around the base of the violet itself. A sucker has the appearance of an entire, very tiny, new plant. Individual leaves are not suckers.

I'm providing a link to a photo of a tiny sucker which appears as darker green in the center of the photo. This should help you.

Elaine

Here is a link that might be useful: Tiny new sucker forming