The day is the next “deadline” for that goal, and the number in green with the little plus sign is, essentially, how much will be “due” that day. Looks like you’re ahead of both your goals, with several days of safety buffer! So, you have until the end of Saturday to do another 0.25 miles, and until the end of Wednesday to do another 4,054 steps.
You can see that my goals are riding a little closer to the line…
I have three colours of “plusses” to show how much I’d have to do to gain different amounts of buffer: for my special-fields goal, for example, I have to do 40 minutes of work by 3am (i.e., in the next 23 hours) to avoid getting charged. If I do 2 hours 23 minutes of special fields work today, I’ll have built up enough buffer to take tomorrow off. If I do 4 hours 6 minutes, I can take two days off. Does that make sense?
The deadline for the whole goal itself (if it has one) will be on the graph, and you will probably have to zoom out to see it. It’ll look like a target: