"Heavily discounted" ... ? (updated)

I thought that the line was when the game was available in a bundle at the equivalent of 15% or less than its full price?

95% indeed, I remember when we had issue with Humble Monthly values, at one month being in limit, other not

I don't know if things have changed, but I remember reading years ago that it is 95%, but it not is set in stone, it is kind of up to the discretion of the one support member that adds games to the bundled list. From what I have seen, it seems like they try to stay very close to 95%.

Also, the discounted price in all countries is considered. The discounted price is converted to US dollars and then compared to the full US retail price. So if the game is 88% off in the US, it could still get bundled because of a currency somewhere else, like Russia. I tend to consider anything 85% or more off in the US to be risky and will probably get bundled because of the price in other currencies.

It give no clear answer because it isn't so easy with XX% because many currency zones.
Something that is -95% in France don't need to be -95% in Argentina and so on.
As general rule you can say -95% because it is the nearest and easiest way to look at it.