Rolling Barrages in FWW

[Der Landser]

I am trying to correlate the information given in the Rolling Barrage dialogue to the distance the Barrage will advance each turn in order to keep my troops safely behind the advancing Barrage. The example below is from the Getting Started scenario.

Allied Powers, From: 06:05 26/9/1918 to 06:30 26/9/1918, Start Line: (0,10) - (8,10), End Line: (0,1) - (8,1): 3x3: 155mm Howitzer
Allied Powers, From: 06:05 26/9/1918 to 06:30 26/9/1918, Start Line: (8,12) - (15,12), End Line: (8,1) - (10,1): 3x3: 155mm Howitzer
Allied Powers, From: 06:05 26/9/1918 to 06:30 26/9/1918, Start Line: (15,12) - (22,12), End Line: (15,1) - (22,1): 3x3: 155mm Howitzer
Allied Powers, From: 06:05 26/9/1918 to 06:30 26/9/1918, Start Line: (22,11) - (30,11), End Line: (22,1) - (30,1): 3x3: 155mm Howitzer

So, this Rolling Barrage starts at 0605 and ends 6 turns later at 0630. The Barrage advances a total of either 10 or 12 hexes during that time. I assume that the Barrage that advances 12 hexes would advance at a rate of 2 hexes per turn. What happens in the case of the Barrage that advances 10 hexes, does it pause at some point for 2 turns?

Essentially, I would like to know how to accurately predict how a Rolling Barrage will advance by analyzing the data in the Rolling Barrage dialogue.