If you have previously displayed explanations for an inference in Protege, and then request explanations for a different inference, the progress panel will display the number of explanations found in the previous usage when it is first displayed. For example, if on the first run it says "Computing explanations. Found 1", then the next time you use it, it immediately starts with "1". So there is no way to know when it finds the first one (I usually wait until it gets to 2 so that something changes).
If you have previously displayed explanations for an inference in Protege, and then request explanations for a different inference, the progress panel will display the number of explanations found in the previous usage when it is first displayed. For example, if on the first run it says "Computing explanations. Found 1", then the next time you use it, it immediately starts with "1". So there is no way to know when it finds the first one (I usually wait until it gets to 2 so that something changes).