It's unfortunate that most people don't understand RNG. The problem is that SE chose to display a percentage figure, which gives a confirmation bias. If we see 99% chance we then expect 99 successes out of every hundred but that's not how it works with RNG (unless you have infinite tries, but even then there's an infinite possibility of failures). Unless you have 0% or 100% success rates shown then you can ignore the value, to all intents & purposes.

TLDR - RNG makes the % value in game as good as useless.