A 'Class A' misdemeanor under WI law is the most serious kind of crime you can commit WITHOUT it being a felony...
WI brakes crimes down into letter-grades:
A: VERY VERY BAD
B: VERY BAD
C: BAD
D: BAD-ISH
E: MEAN
F: NOT NICE
and so on...
I am assuming the Class A midemeanor you are considering committing is carrying a concealed weapon...
In that case, you may be fined up to $1,000, spend up to 90 days in jail, or any combination of the two. Actual fines run the gamut from 'the maximum' to Milwaukee Judge Crawford's $1 (Yes, ONE DOLLAR) fine in the Hamadan case (which is now in front of the state supreme court, challenging the validity of the concealed carry law in light of the state constitution's RKBA ammendment). It's totally up to the judge & DA as to how far they take it.
I hope that answers your question...