I am afraid you won't be very happy with that unit. I am tracing pH meters on several forums (both aquaristic and gardening) and general opinion is that cheap devices show what they want, not what you need.I just ordered a soil ph tester and it also tells you your levels of n, k, p. it was like 20 bucks on ebay.
I didn't have great luck with Hanna pH pens. I'm using Eutech meters now.I have owned a hanna and a oakton. The hanna worked great...for a while.