A theft over $300.00 is not (now) a felony in Maryland. There was a time that $300.00 was the limit between misdemeanor and felony theft, but that was increased to $500.00 several years ago and that point is now $1000.00.
If your charging document refers to "theft over" some amount, that suggests to me that maybe someone was trying to charge you with felony theft rather than misdemeanor theft, which would be charged as "theft under." I would make sure that you don't have a bad copy of the charging document.
But whether you are charged with misdemeanor theft or felony theft, crimes of dishonesty can cause more problems with your life than almost any other type of offense, other than perhaps sex-related offenses, since no one wants to hire or work around a thief. So you need to retain competent counsel to fight the charge and help you obtain a favorable disposition, which I would define a result that will allow you to expunge any record of the charges.