The warning message is to prevent you from accidentally logging out of a character when you don't mean to. The message itself is a bit misleading, but that is because in most browsers now, websites no longer have control over the message that is displayed on a leaving-site warning.
As always, your character progress is immediately saved after every action. You don't need to do anything special.
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Computing the probability that at least one of the following events will occur:
P(a or b ... or z) = 1 - P(!a and !b ... and !z)
Probability
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