According to the Zeiss website:

z600 Standard Hunting: .243, .270, 3006, 300win, 325wsm, etc
Z800/Standard Hunting / ultramag: 300RUM, 3338RUM, etc.

So it appears 3000fps(ish) 600Z & <3000fps is the 800Z. Of course we all know that every rifle is different (fast bore, slow bore, etc)and actual load data vary's greatly (handloads, factory, etc). So this is really a guideline. As mentioned zeiss rapid z calculator website will tell you how to sight in and what each mark represents to your load data inputed. Of course this needs to be verified on the range but it's proven to be pretty good IME with the z600 and my loads in the 338.

The 300 wby would fall into theZ800, according to zeiss.