The soldiers are to present themselves dressed appropriately with sidearms, which I expect is a specific term for certain level of uniform dress. Then the roll is called. Any absentee is determined to be absent without leave and subject to the punishment per the standing orders. In the Navy, the daily allowance of wine or grog could be taken away for a set period of time. In an instance were the order required the roll to be called every two hours, this would limit the the time that stragglers could spend plundering. The punishment aspect is to restrict freedom during periods when duties were light and as such, some soldiers could wander off and plunder. In modern term this would be compared with grounding a child who has broken a house rule.