Do rape statistics take into account the number of unreported rapes?

Do statistics for rape and sexual assault take into account all the incidents not reported? Example: According to the US Department of Justice, 1 in 6 women are victims of sexual assault. But is that one in 6 women will report being assaulted, or 1 in 6 are assaulted, and the number has been already adjusted for unreported assaults based on a statistic saying that x number of assaults aren’t reported? I can’t figure out where to find the info on how they came up with the numbers.