That exponent is still a lot larger than I would've expected for something measured in three digits of atoms. I thought it would've been in the double negative digits.

Yeah. I bet in practice the liquid helium used to cool the trap is more dangerous than the actual antimater. It can cause cryogenic burns similar to frostbite, and if it suddenly boils off in a confined space (like inside a container or the back of a truck) it can displace oxygen and cause inert gas asphyxiation.

Of course both of these can be managed easily with appropriate procedures.

It is a bit like getting injured by pinching your hand in the hinge of the Velociraptor container in Jurrassic park. Not the first danger you would think of, but still present.

Missed opportunity to slap on a big warning label saying "ANTIMATTER CONTAINMENT"