The benchmark is 0 ohms of resistance.
Seriously, you want as low as possible obviously, but every battery is going to have something.
And battery resistance does change with current draw. Is it measuring the resistance of the whole pack, or each cell? If it's each cell, that's pretty high. If for the whole pack, the per cell resistance is 11.6, which is still a bit higher than I would have expected (around 3-6 m ohms). And that's even if the charger is accurate.