I believe you're correct. I think the read out on my treadmill of 25 means 2.5 mph. I've always wondered why the 25 without the decimal. Anyway, I do a very fast walk (don't run) for 20 minutes, sometimes at 1-3% incline. No athlete here, but can attest it gives me energy at my age. The times I skip for a week or two, I'm an old guy climbing the stairs to the bedroom. Where's my automated stair chair lift?
Now, if I only would start working the upper body again. Strangely, just holding the side rails tight while walking builds the arms, traps, lower back erectors, and of course the legs and a little of the buttocks. Fast walks are the best for seniors, plus some light weights for upper body.