That will stickout like a sore thumb when you clear it. I'm assuming that is the edge left when you recoated the quarter. What brand of paint? What brand and speed of reducer are you using? It looks very dry (the edge), like you are using a low quality reducer that is too fast for the conditions.
To fix it you need to do one of three things. First nib sand it with 1000 grit if there is any roughness on that edge. Then spray one to two coats extending out on each side from the edge. This will be hard to do if you are using low grade reducer that is too fast for the conditions. Each coat should be medium at most and each coat should extend a little farther out. You want to have the gun moving before you pull the trigger, and keep moving the gun as you release the trigger, so that you don't have hard stop/start areas.
Second would be to get some blender, mix it with your RTS base 1:1 and do the same. Spray one to two coats extending out on both sides of the problem area. You need to have good reducer that is the right speed. Slow or very slow. Blender is available at your paint jobber. Most base lines have a blender that you can use with the base. Spray the same way as I described above.
Third option if you don't want to buy any additional product, is to mask off the rest of the car, ( you don't want any dry edges) and spray the side again. One to two coats till that area is hidden.