Tableau applies filters and calculations in a fixed order:
- Extract and data source filters
- Context filters
- FIXED LOD expressions
- Dimension filters, including Top N
- INCLUDE and EXCLUDE LOD expressions
- Measure filters
- Table calculations
Two classic surprises come from this. A Top 5 filter and a Category filter are both dimension filters, so they run side by side: Tableau finds the top 5 products overall, then keeps the ones that are camping products, and you see three. And a FIXED expression runs before dimension filters, so filtering Category doesn't change it.
The fix for both: right-click the filter and choose Add to Context. The pill turns gray and the filter moves up to step 2, ahead of FIXED and Top N.