Which "velocity gadget" is it?
Not that I think that's too important in the explanation. If it's the one I think it is, then it is doing the Velocity in the most obvious way.
Velocity is a measure of what you said you would do in a sprint against what you achieved. When an issue moves into the "done" column, it gets counted in the velocity report. If you've set it to report on issue count instead of estimate, then it's just showing you the number of issues that moved into Done every day. It's not looking at their size, just that they got done.
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