How much Aida do I need to leave when framing?

I'm on the last little bit of my Tiny Witch (by DH Morris | TheCozyDH )

I got a frame that has the exact same dimentions as the cross stitch pice. (13x18cm)

I left a lot of space around the pice for it to fit in my hoop (around 20-23 cm). I don't think it will all fit in the frame as it's probably to bulky.

How much do i need to leave around the pice when framing it?

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