You should look in the R80.40 Installation and Upgrade guide where it also references the CLI reference guide in the upgrade SMS with advanced upgrade.
There you will see that the export allows you to include or exclude the logs:
-l - Exports and imports the Check Point logs without log indexes in the $FWDIR/log/ directory.
-x - Exports and imports the Check Point logs with their log indexes in the $FWDIR/log/ directory
So you see the information is available in the manuals.
Next to that when you export without logs your export file, depending on revision databases (which you should remove before running the export) can, from our experience, be anywhere between 50MB to 300MB.
Regards, Maarten