Noob question about magical sites

[Ironhawk]

Sites which offer a bonus to a particular school of magic (conjuration in your case) give you a percent reduction in the gem cost for any rituals cast from that province. So you should be paying only 80% for any conjuration rituals you are doing there. Its not very noticable with the low level summons, as you have noted, but it is quite nice with the more expensive spells.