definiens: means ( i ) if and for so long as the Project Catheters or any portion thereof are covered by a patent or patent application owned by BioScan, and ( ii ) at all other times, subject to the provisions of Section 6.2 . The royalty shall be payable quarterly within 60 days following the end of each calendar quarter . Each royalty payment shall be accompanied by a reasonably detailed schedule of invoiced sales of Project Catheters by [COMPANY] and returns and allowances made during the period and a calculation of the royalties due as a result thereof . In the event of any return of or allowance in respect of a Project Catheter as to which royalty has previously been paid, the royalty on the amount of such return or allowance shall be deducted from subsequent royalty payments . In no event will [COMPANY] be entitled to retroactively adjust the Applicable Percentage with respect to any royalty payments that were already paid