Unfortunately, TargetScan has been initially created for Air Pistol targets where you have a black aiming mark and chamois paper. Over time I did add many more targets, but there are limits I cannot easily overcome. One of them is a very small aiming mark and the other is grey area. The current implementation of my pattern detection module will not be able to deal with this design. There is a target in Netherlands PG50 which is similar, and I also cannot add it.
I will keep this target in my todo list, but it may take a while until it's implemented.