Attempt usually means that it would be one level lower which would make it a first degree misdemeanor, punishable by up to one year in jail. HOWEVER, breaking the window is probably more than an attempt and therefore if the structure was unoccupied, then it is punishable by 5 years prison. If occupied, then up to 15 years prison.
If the building was an abandoned structure, you might be able to get the prosecutor to amend the charge to a criminal mischief. If that is the case, I would imagine that this could be reduced to a misdemeanor.
Burglary Structure is a third degree felony, Level 4. Therefore, Florida Statute 777.04(4)(d)leads me to believe that the maximum penalty for Attempted Burglarly to a Structure is five years in the Department of Corrections (prison) because it would be a third degree felony, Level 3.