This is a point I just dealt with this past Monday.
We were beginning a club night tournament over 4 evenings and we are using an increment for the first time.
When I set my Chronos and the Excalibur GameTime II it displayed the beginning time as 1:00:00, we are playing G/60, i/30.
I set my DGT 3000 and its display showed the beginning time as 1:00:30.
I had a DGT North American handy and to see the seconds had to set it under 20 minutes. When I did it also showed the beginning display as the main time control plus the increment time.
So, I called my FIDE and DGT expert who is a FIDE arbiter that actually runs classes so others can qualify to be FIDE arbiters. He also runs a club in the Chicago area and has DGT clocks that he provides for his tournaments, FIDE and USCF. His name is Sevan Muradian.
Anyway, Sevan told me that this is a FIDE rule on the clock display, and the clocks are supposed to begin with the increment time added to the main control time per FIDE.
Now, we aren't running this as a FIDE event so I actually set my DGT 3000 at 59 minutes and 30 seconds with the 30 second increment. The beginning display, set this way, shows 1:00:00. Now it matches all the other clocks we are using in our event.
It is kind of noteworthy that the Bronstein method of delay, which adds the delay time after the button is pressed also begins with the delay time added to the main time. The DGT NA has US Delay and not Bronstein.
When I set the clock to a control with bonus time, say 3 minutes with 2 seconds increment, the beginning time on the clock is 3:02 instead of 3:00. Is this normal? It doesn't seem like it should be. Is it an option somewhere? I am being careful to set the start time to 3 minutes and 0 seconds and then the increment to 2 seconds. It works normally after that, but there are 2 extra seconds at the start of the game.