Upset by the way computer data is retained (2,4)

I think it could be either:

Which length description are you looking for?:

2,4

in bits

'upset' is the definition.
(I know that upset can be written as in bits)

I cannot understand how the rest of the clue works.

(Another definition for in bits that I've seen is " Broken".)

I've seen this clue in The Guardian.

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