Review the man page for clamscan. There is a setting for “–max-filesize=#n”. This set the max search size of an extraction from an archived (zip or similar) file. The default limit is 25mb. This limit can be increased on the commandline to 4 gb.
What was seen and described above is the message resuling from the scan of an archive file that was larger than the default. This can be made larger as previously described.
I don’t have any experience with this software. However, it is a known “trick” that it is possible to create a small compressed file that expands to something so big that it causes problems. It has been used in denial of service attacks. My guess is that the size checking in clamscan is intended as a protection against this kind of attack.