I may not have the same settings as you with regards to Fit Height, etc.
and so I wasn't able to recreate it with SampleStore.
Would be grateful if you could post your workbook.
One thing you could try would be to create a calculated field of simply: 1
Then you could put this on the Size shelf as MIN([One]).
You could adjust the size slider as needed.
Attached in the Forum thread is a workbook v10.3.
278159size.twbx 1.2 MB