I do not know if this bad math was AI generated or the person was just not thinking. But this stuff scares me as people lean more and more on AI to generate quick and dirty products.
99% off a $100+ order! (capped at $10).
It might be just an example of Hanlon's razor since 25% is close enough to the effective 21% max off (if you spend exactly $70). But really this is a "$15 off orders >$70" discount.