Okay...
How many drone racks do you have on your ship?
Because if you have 56 drones in the supply dock, that is the total for all the launchers on your ship.
Since you can only read the drone supply on a per-rack basis, it probably will always be less (unless it's a 1 drone rack ship)
Also, I'm interested? Is this stock, a modified shiplist like OP+ or something of your own creation.