I like to think of it as an order of magnitude increase for each 9. Ex. If getting to 90% coverage takes 10 hours, getting to 99% will take 100, getting to 99.

I like to think of it as an order of magnitude increase for each 9. Ex. If getting to 90% coverage takes 10 hours, getting to 99% will take 100, getting to 99.9% will take 1000, etc.