I just read that parameter name on the ReceiveSignedBytes block, and see how you just asked for 1 byte.
I leave it to you to search through the Blocks pallette for a single byte read. I am not hopeful.
AI2 block pallettes are kept minimal, to avoid overwhelming newbies.
The block you used lacks the smarts to look for a single byte request and to return just that byte. I think that's just as well.
Instead, grab the incoming bytes list into a variable, and wrap that Label assignment with a FOR EACH ITEM IN LIST block over the incoming bytes list, so each item gets assigned into that Label.Text, but you end up seeing only the last item in the list.