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 in-depth campaign action; for instance, attending more than one event. 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, as a result of the service, 20 people start attending a social justice group, then that counts as 20 in-depth actions. If those same 20 people also each write to their local government, that counts as a further 20 in-depth actions, so 40 in total. (As noted above, if one person takes two separate in-depth actions, that counts as 2 in-depth actions even though they were done by one individual.)