This indicator counts the number of actions taken, not the number of individuals who take action. This means that one individual could take more than one simple campaign action; for instance, signing more than one online petition. The main reason for counting actions, not individuals who take action, is that it tends to be much easier to count the actions taken, than to try and identify which individuals have taken more than one action and filter those out.
This indicator does not count the number of actions you, your partners and allies take - rather, it counts the number of actions that other people took in response to your activities. It also does not simply count the number of people you communicated to as part of your campaign, but only the number of actions that those people went on to do. For example, if you speak at a church with 100 people attending, you cannot count this as 100 actions unless those people actually took an action in response. (As noted above, where it is not possible to count such follow up actions, you can provide a reasonable estimate.) If, at the end of the service, 50 of the 100 people sign a petition, then this counts as 50 simple actions. If 25 of those people also stay behind after the service to pray, then that counts as 75 simple actions. (As noted above, if one person signs the petition and also prays, that counts as 2 simple actions even though they were done by one individual.)