Depending on muscle fiber ratio and training experience there can be a lot of variation relative to the charts.
In fact you can use the80% test to estimate your muscle fiber dominance. You try to get as many reps with your 80% as you can. The number of reps you get gives us a clue about your fiber dominance (at least in the tested muscles).
Traditionally…
80% of max
3-4 reps = VERY fast twitch dominant
5-6 = fast twitch dominant
7-8 = High proportion of fast twitch and intermediate fibers
9-11 = High proportion of intermediation and slow twitch fibers
12+ = Slow twitch very dominant
Training experience also plays a role… if you have always trained using low reps, you will be more efficient with low rep so you will get less reps with 80-85% than the chart says (as well as with other percentages). If you have always done higher reps you will be better with higher reps and you might be above what the chart says.