Files larger that 30mb are not scanned with gatelets.
ContentIQ scan limit is 100 MB file size for securlets, 30 MB file size for gatelets.
Files larger than these will be not be evaluated for a DLP policy.
A file >30 MB would not be sent to DLP for a Data in Motion policy but, if there is a securlet, the file will be send the file to DLP for inspection.
A CASB data transfer policy could be set to block these larger since they are not inspected for content.