this is expected, in 10.5.1 released last week , we have introduced the ability to provide custom sampling rule to be applied to the issues SQL statements for the JDBC Scanner.
you will have to the following as custom parameters:
if you are not yet on 10.5.1, you should consider upgrading to it.
What impact does this have on displaying the value frequency. I see that if the JDBC custom option -DcustomSampling='limit 1000', overrides what is set on the data profiling sample (first N or random), does the Similarity profiling setting that has reuse Basic Profiling setting gets overridden as well ?