Why is the ratio of 1:9 to mAP@0.5 and mAP@0.5:0.95 as the best pt file

[gaodaren47297]

hello，I always have a question：Why is the ratio of 1:9 to mAP@0.5 and mAP@0.5:0.95 as the best pt file，when I training,mAP@0.5 is
Basically stable while mAP@0.5:0.95 is still increase，but the object loss of val datasets begin increasing。
（my English is a little poor,I hope I have described my problem clearly）