(# of soldiers * individual attack (or defense) strength)/50 will give you your ally bonus for a specific building. ex: A lv1 forge at full strength gives you 500 soldiers, each one has an attack of 120 and defense of 60. what does this add to my ally bonus? lets find out (500*120)/50=1200, so a lv1 forge adds 1200 to your attack ally bonus (500*60)/50=600, and 600 to defense this can be helpful when upgrading or building new land what do potions add to my ally stats? simple: potions attack (or defense) strength/50 ex: scroll of death has a 75000attk so; 75000/50=1500, 1500 is added to your attack bonus for that hit. towers are same as potions when figuring your ally bonus; lv1 defense tower adds 30000defense (i think) so 30000/50=600, this is helpful because tower bonus wont show up on your profile (according to the beginners faq)
I don't use it to see my whole ally bonus, that would be a very inefficient way to see my ally bonus, I use it to see the bonus specific buildings/pots give, and what upgrades and new buildings will add to my bonus.
I am a newb, and it is intended for newbs, probably went a little overboard with the detaill, wouldnt expect a veteran player to benefit from it =)