The meaning of "may not be"
What does a phrase like "Such changes may not be major" exactly mean? The full sentence is ""Such changes may not be major, but it is always advisable to check the website for the latest information". Does it mean "the changes can't be significant, they necessarily must be minor" or "the cahges can be either minor or major"?

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Jordan is correct.

"Such changes may not be major" = the changes, if they occur, might be just minor changes

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I'd like to see the full context of this phrase. Out of context, to me it implies that contrary to what one might expect, the changes might very well be minor or subtle.

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