To make it clear - when it offers you the option to exclude the file, folder or whatever it is that has been blocked it means, or should mean, that AVAST will no longer treat it as potentially malicious. In other words it will, or should be, added it to the exclusion list so when AVAST scans it the warning pop-up will, or should not, appear.
The problem with using the word exclude in this case is that it could cause just the sort of confusion the OP describes. It could be understood to mean either the "intruder" is, has been or will be excluded ie. blocked or, alternatively that you're being given the choice to exclude it from future AVAST scans so the warning message doesn't recur. In this case, as dprout69 explained, it is the latter.
Using a less ambiguous term would be one solution or, better, simply provide a fuller description in the pop-up of what has been or will be done and what options, if any, there are. That way there is much less chance of confusion.
