At the provided scale, the inner diameter of the claw is 10mm. Scale it up to fit your use case.
To make a thumb claw, I also scaled the model down in the Z direction so it would be stumpier.
Normally I would provide a source file so you can tweak your own, but this was done hastily in SOLIDWORKS so it's not as ready-to-hack as I'd like it to be.
The author remixed this model.