Maybe - if the PSI of your filter is 20 immediately after cleaning.
In general, what he is saying that that you clean your filter and note the pressure in PSI.
As the filter starts to get more and more dirty the pressure will rise because it will be harder to pump water through the dirt in the filter.
So, let's say your PSI when the filter is clean is 10 PSI.
You should backwash when the PSI is 25% more then the clean PSI.
10 x .25 = 2.5. So, if your clean PSI is 10, then you should backwash when the PSI goes above 12.5
If you clean PSI is 20 then 20 x .25 = 5 so you would backwash when your filter goes above 25 PSI.
Make sense? Did you clean your filter yet? If so, what was the PSI immediately after cleaning?