Don't listen to Sirius

.
The problem with his suggestion is that it is good advice for film that is sensitive to the same light that our meters are sensitive to - visible light. So if you use the film for normal photography, go ahead and follow your meter and all that manufacturer's advice.
If you use a 720 nm filter, you are blocking out almost all the visible light, and letting just a little bit of the infrared and near infrared light through.
At the same time, you are metering the visible light with a meter that doesn't really read what the film is going to be exposed to.
The reason that you bracket is that there is a complex correlation between how much visible light that is around, and how much near infrared and infrared light there is around,. That correlation is affected by factors like time of day, season and the condition of foliage which happens to be one of the best reflectors of near infrared and infrared light. The results of that bracketing help you build your database of information about that correlation.
Sirius' suggestion for how much filter factor to use is fine. You need to use the bracketing data to build on that.
A somewhat informative example using Ilford SFX, a not quite as infrared film as the options branded as Rollei:
https://www.photrio.com/forum/threads/choices-for-ir-film.174757/#post-2273526