Probability field is behaving in very odd manner

Probability field is behaving in very odd manner

Even though I have not been filling in the probability field, I just noticed that all my deals have a % shown in that field, with apparently random amounts. Any idea what is going on? Again, I have not entered anything so this field should be blank. A friend of mine that uses Bigin is having the same issue so I hope someone can help me get to the bottom of it.
thanks