Documentation needed for using Parameters in SQL Server Connector

I would like to have our SQL Server Connector import only data that has been altered since the last successful import (something like dtLastUpdated >= _BATCH_LAST_RUN_, but only if that value is only saved on a successful import. In the Details section of the connector there is a Query Parameter option that hints at this being possible:

Enter the query parameter value, it is the initial value for query parameter. The last run date is optional by default it is '02/01/1700' if is not provided. For example: !{lastvalue:_id}!=1,!{lastrundate:start_date}!=02/01/1944

Unfortunately that doesn't exactly explain how that works, and I cannot find documentation on query parameters anywhere. Is what I want possible (with parameters or some other method), and if so can anyone point me to documentation on how to use it?

Thanks in advance …