For MySQL Query Explorer, for Query Monitor View: When the Sampling Frequency is set to (for example) 30 sec, it samples queries once every 30 seconds for as long as it needs to collect the information of all running queries for that snapshot. Let's say that this takes 1 second. So, it samples queries for 1 second and displays the results. 30 seconds later it samples queries for 1 second again and displays the results. Etc. It does not sample queries during the 30 second time interval. It only samples queries for 1 second and then it does nothing for 29 seconds.
Note that MySQL Query Explorer can sample queries that are running on the connected instances of MySQL, and that it can display results for a manually entered query.