Table summary row incorrect

I'm debugging a data issue in Looker Studio: To test something I've built a very simple standard table in a completely fresh report with no other filters, blends or charts, however the summary row in my table does not give the correct sum of the columns e.g. below is showing 209 and 210 but should be 222 and 226 respectively - if I click on 'show underlying data' I can confirm that the columns should add up to 222 and 226:

image001.png

Does anyone have any ideas what might be causing this? I though it might be something I've missed as part of a bigger more complex report, but I've stripped everything right back to try and debug this issue.

Many thanks.

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