Note that the first expression is not valid. You may use 'is Not Null' instead of '<> NULL'. It will still count all the occurrences of the field although the inner expression will return either True or False.
The second expression '= Count(Fields.[Inspector Name])' is valid and returns the count of the records in the corresponding scope. I suspect that you use grouping and/or filtering, hence the item number is more than the displayed rows.
If you hide some of the rows with Bindings or Conditional Formatting, you may try using the same expression with the Count function to filter out the non-visible items.
Feel free also to send us a runnable report for local investigation. I hope we will be able to provide a proper solution for the requirement.