Not enough information to actually be useful. Did you scroll down the same page and read their ideas for fertilizer, etc. They are saying just an Epsom salts solution is a 'substitute for fertilizer', same with coffee grounds and egg shells. Sounds like the same people who advocate putting ice cubes on orchids . . . they want to sell more plants when you kill off the ones you have.
Good grief, there's a lot of marginal info on the internet.
Forgot to add, I just ordered a soil test kit from Amazon, 10 tests incl. pH and nutrients for $12. It's called Rapidtest, I think, and one of the universities in California tested it against their lab test, found it 94% accurate. That's cheap, easy and is going to give you a lot more good information.