The “formula” word is used as metapho, really. It’s a method of how you structure a database query for this particular browsing. It can be altered relatively easily in the code, but you do need to know what you are doing. If it’s going to be you main browsing page the query will affect site performance significantly and must be structured correctly. Some variables may be more resource intensive than others, too - so I would say it is best to coordinate this with us or with some other experienced developer. We can help though custom services.