As you know damage per attack is damage caused to target when the damage source (in this case the Cannons). As the value shown in the info is damage per second (DPS), you need to find the source that knows the damage source (is troops or defenses, basically) attacking speed. Multiply it with their DpS and you got the DPA. This video will show you that the DPA is NOT rounded at all. Note: Cannon attacking speed is 0.8 second. DPA of the Cannon on the first part of the video is 12 exactly as it's DPS is 15, and upper section cannons' DPA is 8.8 each, OR 8 or 9 if it's rounded. Giant's HP is 670 (my giant is level 5). Calculate yourself.
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