I would bet that at one time the stairs were back under the roof and that is why they have the extra wall there and not in the center of the porch. So that beam might join at that wall below the window.
Look at it like good catch, this could get real bad in another year or two.
The door frame will have to be pulled too so you can add a new aluminum threshold to it. and there is some stud repair there too.
Once you have that white board off you can get the correct height measurement and some good photos before you pull it out, You want to have everything ready for a quick change.
We only have to worry about supporting the roof over the door and that first window