did they send you a photo of the 'blemish'? easy to live with? then you are lucky. you have heard this, determined it is very desirable? return option?
I always am aware that anything I buy will end up with a blemish or two, primarily my doing, so I am a big fan of open box, as long as the full manufacturer's warranty applies. not a blemish I have to see every time I use it, something out of sight when in use,
or, something on the passenger side of the car!!! Next accident I will have that dealt with.
You know they regularly have sales, so that would be 10-15%, then you have open box discount, so I agree, don't ask, make them an offer, figure out -25%, offer them that in writing, i.e. email, with confirmation of warranty and return in that email. that allows them to forward the email to whomever makes the final decision without anything lost in translation.
clarify: credit card? pick your credit card with best protection. option for extended warranty? So, you get a discount, spend it on the extended warranty, sleep easy.
They come back, 20% off, yay or nay? don't forget, any discount/sale, you save tax also, so that helps your final price/decision.
good luck