Make a mistake in telling (8)

I believe the answer is:

miscount

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'mistake in telling' is the definition.
'miscount' can be an answer for 'mistake' (thesaurus). I'm not certain of the 'in telling' bit.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for miscount that I've seen before include "Make error with 20 [ABACUS]" , "total boob" .)

I've seen this clue in the Evening Standard.

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