Stroke of bad luck then, there is no possibility to have the % display correctly but with a % different when it has to be used, this is the same function.
It is not a good move to always try for an ambush, because it can backfire, if the opposing force is particularly well deployed. So 44% does not mean you will do an ambush 44% of the time. This is the average quality of your Ambush preparation, which is then compared to a counter-surprise roll made by the attacked force. This also mean that you are better not set an ambush if the % is too low, because you can fail in such way that you will attack with penalties, compared to having attacked normally (this also answer Willgamer question).