Hi! It looks like your steps are getting pulled in automatically from the apple watch, so that's step one taken care of! Next, getting the road set up sensibly. If you visit your goal page (click on the graph in the dashboard view and you'll get the big graph / goal page view), you can change the road setup on the Commitment tab:
Ok, so here you can set up what you're committing to for each day (this is from my own steps goal at beeminder.com/b/jsteps)
Here you can set the end date, and how many steps you want to average per day. Then Beeminder will automatically pull your steps from your apple watch, and update Beeminder, and Beeminder will alert you if you're falling behind. With my goal of 7500 steps per day, if I do extra and hit 8000 steps one day, then I get to keep that extra -- and the next day my minimum will be only 7000 steps.
But anyway, the important thing is that blip above the graph (or on the dashboard) which says, e.g., "steps: +5130 due in 1days or pay $30" -- I've got a big buffer on steps goal right now from a trip to Amsterdam last week where we did a TON of walking.
Link to my steps goal since I referenced it a ton above: