It's because that's not a standard private key format. In fact, I'm not sure what format it's in, because it's 36 bytes, and unless I did something wrong, it does not look like the last 4 bytes are a checksum. Therefore, Armory interpretted it as a 36-byte integer, which is clearly larger than that 32-byte integer shown there.
I'm not sure what's going on with that key...
Oops, I screwed up with the copy/paste. The real private key is: Kz9Eyg1rL27RnkUmmkofeyxdbWSn7ARQTdCiVKHLKxdhrMGNjTAp
I did some more digging and this is a "private key associated with a compressed public key": "Private keys associated with compressed public keys are 52 characters and start with a capital L or K."
https://en.bitcoin.it/wiki/Private_key