We affirm the trial court’s denial of appellant’s Florida Rule of Criminal Procedure 3.800(a) motion without prejudice to appellant’s pursuing his claim of incorrect calculation of gain time credit before the Department of Corrections. See Green v. State, 698 So.2d 575 (Fla. 5th DCA 1997); Slay v. Singletary, 676 So.2d 456 (Fla. 1st DCA 1996)(en banc), aff'd, 688 So.2d 319 (Fla. 1997); Duggan v. Department of Corrections, 665 So.2d 1152 (Fla. 5th DCA 1996).