Hi gracy,
Sorry, I don't have a definite answer, but I think it's just a convention in statistics similar to the significance levels:10% marginally significant
5% significant
1% highly significant
This article says, such criteria are not "sacrosanct limits". If I may, you may want to give the "mnemonics" like: 10-90 modestly inclusive
5-95 significantly inclusive
1-99 highly significantly inclusive
I found an interesting article here.
Hope this suggests something.
--Hideo Fujii
OriginLab