Allthou there are events that in deed are not present (don't know why), the one you are mentioning is there. Don't remember the name but it works like this: When you have to collect in your Capital, it is proposed to you not to collect with all the hoplites you have in that region (for example 5) and the number you don't use to collect (for example you collect with only 2 of them, leaving 3 inactive) are used to gain points in prestige at a maximun of 3 in this example, but there has to be at least that population (3) in your capital at that moment if not you are going to earn less prestige. In other words to earn the 3 prestiges in our example, you should have 3 population at least in your capital at that very moment, if you have only one population for example, it is useless to collect with only 2 hoplites, you should collect with 4 hoplites, you get only one prestige in any case.