What is the fine-grained topic of the following text: In terms of archer rainbows when hitting lv10 NPC's, a full Lv 5 set will mean about 4,000 Archer losses, lv9 set will mean 3,000 losses and a lv12 set will mean about 2,000 losses. Only return the topic.
Archer loss rates in NPC battles at different equipment levels in a game