The fingering I had for Fm13 was - (x 8 10 8 9 10) Basically a minor 7th with a 6th. The problem is that the 6th (D) is outside the diatonic structure of the key I'm playing in. The proper note for the key would be a Db. Which would make that chord an Fmb13, right?
Right now I'm thinking that whoever wrote this chord chart didn't know what they were doing.