Room is colder than TRV thinks. Offset??

The Tado TRVs think it’s warmer in a couple of rooms than it actually is, and keep switching off. Even if I tell them to heat to 25C they still switch off too early!

Tado Help directs me to an Offset option in ‘Rooms and Settings’ but I can’t see it. Have checked app (iOS) and web version. Can anyone help?!