You could say "I'm subject to hay fever in the Spring" or "I'm likely to have hay fever in the Spring" and there wouldn't be much difference in the meaning. Perhaps "being subject to" suggests more certainty: "I'm subject to his commands" versus "I'm likely to follow his commands". Also the sentence construction is different, so you can't just substitute one for the other.

I think it's like "small change" when you are speaking of money. You might say, " It cost £250 and change", meaning £250 and some pennies. In this case, it would mean "some minutes".