And no, the waitress did not offer to make the adjustment.
She should've made the adjustment! 
I suspect that seniors who ask for the discount get slightly smaller portions
Hum, I hadn't thought of that. You may be right.
Does our resident restaurant critic, DR John G, have any thoughts on this?
I would have taken it up with a manager.
Some days you bother, some days you don't.
I think the question directed at you was if restaurants serve smaller portions if you ask for the senior discount.
That’s why I would have spoken with a manager. Only they can explain why the sign and deal with how to handle the situation. A waitress often has no power to change anything.
LOL, kind of a different subject. DR Vixmom suspects that IHOP, and other restaurants serve smaller portions if you take a senior discount. DR Jeanne was curious if this is true. 
As for our situation, we just wanted to leave and didn't bother.
Yes, it's true for most places. But there's a diner chain I go to that gives you two sides and bread with the senior special and it's nice, especially when I get a double order of the fried okra, which is always better than it has any right to be.
I never considered the portions would be smaller. That diner knows how to do it the right way.
