Yes, you can reserve 90 days before the date of the ADR. If you're not booked into an on-site resort, you must call no more than 90 days before each date. If you were staying on site, you could make the ADRs at 90 days for the next 10 days.
Let's say you wanted to make ADRs for Sept. 7-12. You don't have a hotel booked. You can call today (June 9) and make an ADR for Sept. 7. Then tomorrow, you can call and make an ADR for Sept. 8, and so on.
If you are staying on site, you can call today (June 9) and make ADRs for Sept. 7, 8, 9, etc. all the way to Sept. 17, 10 days following the first 90 day mark.
Does that make sense?
If you're talking about late July, however, you can make all your ADRs now since it's all within the 90 day window.