The correct approach would be to say something like "Previous experiments reported X, we observed X + Y, therefore the real answer is probably around X + Y/10."

The correct approach would be to say something like "Previous experiments reported X, we observed X + Y, therefore the real answer is probably around X + Y/10." But it's very important to state the observation of X + Y, not X + Y/10, otherwise you'll take much too long to update to the correct value!