In a normal "single room zone" there is only one temperature sensor used for the zone. Because you added a YT87 as temperature sensor to the room this is your active sensor in the room, and the built in sensors in the HR92's will not be used, except for the open window detection feature which looks for sudden temperature drops to detect a window being left open. But for normal room temperature regulation only the YT87 reading will be used, and all HR92's in the zone that are set to show measured temperature will just display the same temperature reported by the YT87 and controller.
Why would you want to show the temperature measured beside the radiators when it is nowhere near as accurate as that reported by a remote YT87 ? That's the whole point of using a remote sensor...
The calibration offset configured in the HR92's does nothing when they are not being used as the temperature sensor. The YT87 itself might have a calibration setting (not sure, as I don't have one) but generally a calibration offset is not needed for a remote wall sensor because it is not subject to heat from close proximity to a radiator.
The system measures the temperature to a full two decimal places and uses this precise value when trying to regulate room temperature, however it is only displayed rounded to the nearest half degree, and is also biased up to half a degree towards the set point.