I think if you're just walking steadily on it without trying
to break it (like jumping up and down on it, but who does that?), you'll be fine for a few months.
It might put a little more wear & tear on the tread or something, but I don't think it has to sit in a corner collecting dust until you lose 21 pounds.
Also! Welcome to 3FC and congrats on your work so far! That's very exciting to see. I'm also a WW member, and I use my Treadmill pretty much daily