Understanding how the databases fill?

Why are the databases so unbalanced. Is this how this works. We have about 35 sites established with content. _crow is the original plugin for wordpress. Why as we add content & sites the only number that seems to change is the _crow database.

Also why is the other databases set at values of 9 & 18, then you have the global sitting on the number 17? Just curious if any one can answer this.