First TY to make a try on my scenario and sorry for my poor English if some special rules are not clear.
At the start of his turn, the Allies player rolls a die. If the result is NOT a flag, he advance a count 1 by 1 (use anything to count or the counter on the side of the board if using Vassal). When rolling a flag, the count do not changes (the Prussians are late). When reaching 7 and 9, the Prussian reinforcements arrive as described!
Hope this helps?