Black/Grey Water pumbing confusion

[KrowNB]

We bought our 2017 Hideout 25RKS late last year and never really had a chance to figure things out before winterizing. I have two grey tanks, one for the rear kitchen and one central for the bathroom. In dewinterizing it today, flushing lines, etc, I ran water in the bathroom sink and watched to see which grey tank filled by watching the panel to determine which is labelled Grey1 and which is Grey2. Both tanks started out empty as was the black. I kept switching he button from G1 to G2 but the indicator stayed on empty well after I thought there should be a reading. I then pressed the black tank button and, low and behold, the indicator showed 1/3 full! So, the bathroom sink runs into the black tank, not the grey! The shower drains to the grey tank (G1) and the kitchen sink to G2.

I can't see how it makes much difference - a bit more water in the black tank can't hurt. Just wondering, is this setup (bath sink to black tank) normal? Are there potential problems that aren't apparent?

K