Definitely the wrong bracket for the application. Did you change the seat or just get the brackets.
Order the backrest and it doesn't fit because I have a different non stock seat place I ordered it from knew it wasn't stock but let me order it anyway and this is what I'm stuck with at the moment.
Are you certain that the fender seat is mounted in the correct position ?
Using the single bolt hole.
Maybe you can make an extension for the seat mount and move it forward, it looks like you have some room there
You might be able to do the same with the back rest mount. I have a machinist friend that can make anything out of metal. I bet if you hit a machine shop they could make a small plates to relocate the holes for the back rest back an inch or so. Try contacting the manufacturer of the back rest and sending them the photo. They may have a different bracket.
This what i did
They did that to keep the fat girls off your bike lol
And keep the skinny ones up close