Theft is an enhanceable offense, meaning that prior convictions, even Class C (fine only, like a ticket) convictions, make the next charge a higher grade of offense. Normally you get 2 convictions before it becomes a state jail felony, and if you were to keep offending and had received a State Jail sentence then you could be subject to even higher penalties. In this instance there is another applicable enhancement, that with a prior conviction for any grade of Theft, even a Class C, which is normally for items totaling less than $100 it becomes a Class B misdemeanor, punishable by 6 months in County Jail and up to a $2000 fine. The IAT part of the charge means "if at trial," meaning that the prosecution would have to prove it at trial in order for it to be a Class B. Because different courts have jurisdiction over Class C's versus Class B and A misdemeanors, this is a jurisdictional element in this case.