Pivot Table: Hiding Zero Values Also Hides Negative Values

Sadly I am unable to share a copy of the sheet in question and I haven't the time to anonymize the data:

I've got a pivot table producing a stock report from a ledger.
The rows are the Garment field broken down by Size.
My columns are In, Out, and a calculated item (Garments In - Garments Out), which creates a row for every size, even if a garment doesn't come in that size.
Because of this there are lots of sizes for which the sum is zero, and I use a value filter (Sum of Qty does not equal 0) to hide these rows.

This generally works fine unless one of the quantities is negative, which happens, usually because of a data entry error.
For some reason the negative values gets swept up with the zeros and those rows are hidden.
As far as I understand it, zero means ZERO and nothing else, but perhaps these filters work differenty.

Is there any way I can filter out the zero sum rows while leaving the negative rows alone?

I need them in the report so that I can spot the error and correct the ledger.

Welcome to the forum

Please attach a sample workbook (not a picture or pasted copy). Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.

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Is it really a calculated field, or a calculated item?

The filter will filter out rows where the sum of all three columns is 0. So if say In is 0 and Out is negative, then the difference column will be the same as Out but positive and the sum of all three will be 0. Would that explain what you are seeing?

Since you have 365, you could load the data into the data model (via Power Pivot) and create three measures to do the calculations for you. That should avoid all the problems that calculated items cause.