Cannot apply fractional scaling

I am connecting GNOME desktop of Ubuntu 22.04.3 LTS in a remote server through TigerVNC. If I turn on Fractional Scaling in Display Settings and select a fractional scale, say 150%, this fractional scale will spontaneously change itself to an integer scale, say 200%, when I click "Apply" button. Is it a bug? If not, do you know how to set a fractional scaling in this scenario? Thanks.

This is a screenshot: https://ibb.co/DRxqGyX. GNOME version is 42.9. TigerVNC is 1.12.0.