Welcome to the site !!
Oil kind of depends on the oil you use and the riding conditions ..... Basically , if you ride in dusty conditions , you should change it more frequently , if you rev it a lot , if you are racing (not so much for a trail bike) , and whether you use Petroleum or Synthetic or a blend of both .. whether you ride in extreme heat (slow hot day riding in first gear where the engine is going to run much hotter than if you were tooling along at 20mph in 3rd gear and air was keeping the engine temps down)
Basically the manual is a recommendation , but not set in stone .... I have always ran full synthetic once the engine is broke in , so I can get away with longer intervals , but for a example , as your Manual says , my 2020 CRF450R Manual says , 15 hours for the oil change and a Piston .... ok , if you race hard , if you rev it to the moon , and if you are using Petroleum oil , that might be necessary , but I am not racing Pro Motocross I ride hard , but I am far from pushing the bike to its limits .... I change mine (using full synthetic) every 10 hours , in my trail bike (06 450X) I change it 2 -3 times a season ... period , it is not abused , and the conditions I ride it are not as dusty as with my MX bike , though sometimes there is dust , I am not revving it constantly like I am with my R , and I am using the same full synthetic as my R , which allows you to run a bit longer
Here is what I do for changes .... I look at the oil when I change it , if it looks dark and dirty , I change it more frequently , if it is staying clean , then I know I am doing fine ... if the oil is dirty , it is in need of replacement period , regardless of hours or conditions .... consider the oil as the food you put in your body , if you eat crappy food , your body pays for it , as do you , you have more medical issues , which means more maintenance to fix things that are damaged ... if you eat somewhat healthy , you can do more and feel better when doing it , if you eat really healthy , you can look forward to a long and enjoyable life ...... same goes for your bike , what you feed it , is how it will live .....
There is no set , change your oil with this timeframe , or use this oil , that is all speculation and preference , do what your budget allows , do what your riding necessitates , and you will be fine ....
