What's the actual risk of getting pregnant compared to the advertised effectiveness rate of the contraception method?

For exemple, birth control pills are advertised as being 92% effective. What does that mean? That (theoretically) if a user was to have sex 100 times they'd statistically get pregnant 8 times? That seems really high. Else, what does this number mean?
If you use birth control perfectly, the pill is 99% effective [1, 2] However, people aren't perfect and it's easy to forget or miss pills — so in reality the pill is about 91% effective [1]. That means about 9 out of 100 pill users get pregnant each year [1, 2]. The effectiveness of birth control is also dependant on the type you use and whether or not you use it correctly [3, 4]. The pill is 92% effective at preventing pregnancy and Depo Provera is 94% effective [2]. Effectiveness of different contraception methods is measured by how many women will get pregnant within a year of using that method [2, 3]. Hormonal intrauterine devices (IUD) and hormonal implants are the most effective forms of reversible birth control [4, 5]. Once inserted, the hormonal implant and hormonal IUD are more than 99 percent effective at preventing pregnancy [4]. Overall, birth control can be an effective way to prevent unintended pregnancy, but no method is 100 percent successful [4]. 
The failure rate for birth control methods is the number of pregnancies that take place when 100 women use that birth control method for one year [1]. So, for example, if a birth control is advertised as being 92% effective, that means that about 8 out of 100 women will get pregnant each year if they don't always use the pill correctly, and about 6 out of 100 women will get pregnant each year if they don't always use Depo Provera as directed [1]. However, the effectiveness rate for birth control methods is the number you get when you subtract its failure rate from 100 [1]. Therefore, the actual risk of getting pregnant compared to the effectiveness rate is roughly 6 out of 100 women will get pregnant each year if they don't always use Depo Provera as directed [1], and about 8 out of 100 women will get pregnant each year if they don't always use the pill correctly [1].