Is the default 500 MB usage valid for log of sourcetype other than fixed sourcetype of license?

I have a single Splunk instance ( No master slave configuration ). Our Splunk license is for a fixed sourcetype. If I try to add a log file ( less than 500 MB ) of a different sourcetype ( other than the fixed sourcetype of license ), Splunk throws a license violation.
How can i allot the default (free) 500 MB usage for this second sourcetype?
Any help appreciated.
Thanks in advance.