I wouldn’t trust that reading if it’s at the start of fermentation. The starter liquid should just drop it into the range of preventing spoilage bacteria, so 4.5-ish at the lowest. I wouldn’t invest in a pH meter for just kombucha, since the process is pretty much failproof. If you’re going to use it for beer, that’s a different matter and budget for around $100 to get a good reliable one. For kombucha, though, I think you can get away with taste being the indicator.
How large was the scoby that came with your kit?