Lightroom object mask working reverse on Mac

Hi everyone,

I'm experiencing a strange issue with Lightroom Desktop on my Mac, and I'd really appreciate any advice.

Whenever I go to Masking > Objects, I select my subject, but instead of the selected subject being masked, the background is highlighted in red. However, when I adjust the Exposure slider, it's actually the subject that changes, even though the background is the area highlighted.

It gets even more confusing when I click Invert. The subject then becomes highlighted in red, but when I adjust the Exposure slider, the background changes instead.

So, the highlighted area and the area that actually receives the adjustment seem to be opposite of each other. In other words, my masking appears to behave the exact opposite of what I intend.

Has anyone experienced this before? Is this a known bug, a display issue, or have I accidentally enabled a setting?

Any advice would be greatly appreciated. Thank you!