Yes, if you have 28 day cycles you can take P from day 15 (or 16) to day 26 inclusive and then stop and that should trigger a bleed. If you bleed early, you have to make a call as to whether it is breakthrough bleeding and you should ignore it and just keep taking the P through it, or whether it is your period come early - and you should stop the P and allow it to happen.
It can take some experimentation. I used to continue the P but if the bleeding continued or got heavier after a day or two, I would stop the P and log it as day 1 of my next cycle.
If your cycles get much shorter, you will need to switch to more of a continuous schedule as I said above. Because you need to get enough P in, each cycle. If you are only taking P from day 16-26 but you are starting to bleed (with a period) on day 20 and you stop the P, you would only be taking it from day 16-20 - for 5 days. Which isn't enough to protect you.
Which is why, if your cycles get a lot shorter, you need to be creative with the P use and switch to taking it almost continuously except for the 5 day break to bleed. Some women can take it continuously without that break but if you are still in peri the risk if you will bleed randomly and worry doctors and get referred for scans etc. So I think the 'almost continuous' thing is a good solution for late peri. You can get enough P in, each short cycle, taking it from day 5 onwards and you also have more of a regular bleeding pattern. Hope that helps.