Sec. 2.6. (a) Except as provided in subsection (b), as used in this chapter, "gross retail incremental amount" means the remainder of:
(1) the aggregate amount of state gross retail and use taxes that are remitted under IC 6-2.5 by businesses operating in a district during a state fiscal year; minus
(2) the gross retail base period amount;
as determined by the department of state revenue under section 14 of this chapter.
(b) For purposes of a district designated under section 12.1 of this chapter, "gross retail incremental amount" means seventy-five percent (75%) of the amount described in subsection (a).