Yea I thought that would be the case, they generally come longer than needed so that anyone can use the supplied set.
Do you have clips on it or tying on? If clips it’s very easy to whip them off, mark say 5 or 10mm on each one and cut then try them out and see how they feel, can keep going until your happy with how they feel. I wouldn’t max them out fully as they won’t last as long and it’s not necessary for target shooting. If it’s stretching an extra 6 inches you will probably want to lose around an inch but I would go in small increments at a time as you can’t put it back on!
Just make sure when you do, the cuts are straight and the same amount is coming off each side, a rotary cutter is best but carefully with sharp scissors can work