It would seem that all the methods seem to overcharge for extra creatures conjured, the book seems to imply that the added complexity is a factor of size and quantity combined so summoning a dog the size of a bus would cost the same as summoning a dozen dogs that add up to the size of a bus, since all the individual constructs exist under the same rules all you are really doing is using more energy to replicate the exact effect multiple times requiring only more energy not more consideration from the caster. so based on that half a dozen dogs about 4x6x2 at would add up to roughly the size of an SUV which would only be about one step up in size from a normal car would mean a +4 for more than just one, from that creating the guardians as such
High concept: Conjured guardian
Skills: +3 might, endurance
+2 fists, intimidation
+1 Alertness, Athletics
Powers: Claws, Inhuman toughness/speed/strength
1 mild and 1 moderate consequence
using the Fred Hicks method
http://www.jimbutcheronline.com/bb/index.php/topic,23624.15.html the final cost would be 6 for stress+6 for consequences + 10 for powers (not paying for toughness twice) you get 22+4 for quantity with duration already worked into the ward add 2 to have a condition and it would be built in similar to how you could build in any other spell effect (like a divination as is suggested in YS) becomes 28+8 for the basic power of the ward+4 for other conditions+10 shifts to increase duration to a decade makes for a 50 shift ward total.