A consumer may not understand that but a regulator would. It's not like you're saying $100 cash and only giving $50. I can't imagine you been accused of deceptive advertising for that, but of course all this is just my personal opinion.
Not that this makes it right, but I think all banks do it all the time. If you feel the need, you might just put something in the fine print about full value will be reached after 7 years maturity.