Grabbed a $30 iTunes from the gift card display which was labeled 15% off. When I got to the checkout there were 20% off iTunes flyers (6 march to 8 march). Was curious as to what it would scan up as and to my shock it double dipped the discount.
Might be other stores too, but can't validate. As the 20% flyer ends today the 32% will only work today.
I think you were lucky OP.
Just went to 2127 Woolworths to give it a try and it doesn't work, $30 card scanned up for $24, so only a 20% discount.