Casey Anthony's Lawyers -- We're Appealing Her Probation

Casey Anthony's legal team tells TMZ they will fight the judge who just rejected their claim that Casey served her probation for check fraud while she sat in jail during her murder trial ... and if they lose Casey will have to return to Florida in 11 days.

Anthony was sentenced to 1 year's probation for her 2010 check fraud conviction. The judge who sentenced her said in court the time Casey spent in jail would not count toward completing probation, but the order the judge signed mistakenly allowed Casey's probation to run concurrently with her time in the pokey.

A judge ruled on Friday that the judge who sentenced Casey clearly made an innocent mistake, and it wouldn't make sense to allow Casey to get credit for the time she was in jail. After all, the point of probation is to test how a person behaves when they are in the real world, not while they're locked up with few opportunities to misbehave.

But now her lawyers tell TMZ they will appeal Friday's ruling. If they win, it would mean Casey would get a huge break -- her probation would already be completed -- because of a technical error.

Casey's lawyers say if they lose their appeal ... they want her to serve her probation in a state other than Florida.