I think you are referring to the sentencing guidelines. The priors are scored along with the current charge. He should consult with an aggressive criminal defense attorney.
In Florida a Criminal Punishment Code Scoresheet is used for Felony charges to determine possible sentences. If an individuals sentence points are less than or equal to 44 points they are in what is often referred to as NSP or non-state prison sanctions. However, that does not mean the Court/Judge cannot still sentence them to state prison. It does give the Judge descretion to sentence one to Probation/House arrest or county jail. The scoresheet is 4 main critera: 1. primary offense 2.additional offenses 3. victim injury 4. prior record. The scoresheet is something that really needs to be discussed with an experienced criminal lawyer in your area to exactly determine how many points your father may have. His prior record will definitely be scored however, the primary offense is wwhere the bulk of the points will come from. The Primary offense is based on what Level crime is charged. In this case Felony Battery is the Primary offense and an experienced attorney can tell you what level crime that is.
If your dad has not had any crime within the past 10 years and has not been incarcerated or placed on any kind of probation in the past ten years, then technically his old record should not be scored on the guideline sheet. But the guidelines only set a minimum sentence, which means that the judge could sentence your dad up to five years, regardless of what his guidelines are.