Your might does not increase with each technology level by the net amount indicated in the upgrade breakdown. Rather, this breakdown reflects a total of might that each level grants you. Hence, what will be added to your might is the difference for the two levels (e.g. if a level 10 technology grants you 15K might and level 9 yields 7K, then upon upgrading to level 10 you will not receive 15K might net, but rather 15K - 7K = 8K additional might).

The same logic applies to building upgrades.