[I know I can't control anything in that panel but I had to choose a name for it.] When I enter math.stackexchange.com I can see a page (I'll call it p1) with a bar on the top containing, on the right side, a square and my reputation number by the side of it. I click the square and find my self in another page (call it p2). In p2 there is a list of post titles under the heading "Reputation" (right hand) having, on the left side of each title, a number. Is there any relation between this number and the big number appearing by the left side of the OP in p1? Or, more generally, what is this number? The same question could be asked with respect to the numbers listed under "Questions" (left hand) in p2.
The number in the top bar is the total of your reputation points on the site (these are 437 at the moment). Having many points gives you additional options on the site; for example once on has 50 points one can write comments, once on has 2000 points one can edit other users posts, etc. See https://math.stackexchange.com/help/whats-reputation for an overview. Mostly you get those points based on how your posts are received by others, which they express by votes (up or down) the difference is the score of the post, which is displayed next to each post.
The second page you mention is your user profile page
The numbers on the right are likely your recent point changes. The number in the topbar is just the sum of all those events.
The numbers on the left give the score of the post. The points gained from a post are tightly correlated to the score.