Month to go over nearly everything to do with numbering system (5)

I believe the answer is:

octal

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'go over nearly everything to do with numbering system' is the definition.
I can't judge whether this defines the answer.

'month to' is the wordplay.
'month' becomes 'oct' (Oct is an example).
'to' becomes 'al' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'oct'+'al'='OCTAL'

Can you help me to learn more?

(Other definitions for octal that I've seen before include "that must omit a couple of digits" , "with unusual base" , "(Of numbers) in base 8" , "type of base" , "based on ...[EIGHT]" .)

I've seen this clue in The Telegraph.

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