CM requirements

I just did the Wand Gem Upgrade 1 for a Crystal Lightning Wand and had both a 5.00cm and 10.00cm Garnet on me when it only needed a 1.00cm+. The upgrade ended up using the 5.00cm instead of the 10.00cm. Would it be safe to say that any gem closest to the exact value the upgrade needs would be used up instead of the highest size you happen to own? If so, I think that would be worth mentioning on this page so that some people don't have to worry about the higher size being used up.

It takes the gem placed nearest to the bottom right of your inventory, I've had many instanced when it took the 10cm one rather than the size closest to the demanded size.