Your total "Domains on Blocklist" could be considered pretty low. The youtube tutorial on the original post provides some good information and has a link to some nice categorized block lists. There are also several other references for blocking lists on the Pi-Hole community.
Currently I have about 900,000 on my blocklist. This is not close to what is possible and certainly not a recommended number. I am just providing it for reference. With the list I have, the percent blocked bounces around 15-20%. Also consider that the amount of blocked queries is only applicable to your usage. If you have a blocklist primarily for malware domains, but your internet usage stays in the safer domains, then you wont have a lot of hits. If you are blocking adverts and do a lot of online shopping, that hit count is going to shoot up.