That's a high impedance sense line, so no current is going to it (It's the reference voltage for the charge pump). It's isolated up to 80v (Hence the 80v rating) so the controller won't care what sort of currents are flowing through the H bridge as long as the voltage doesn't exceed 80v (which it won't in your application).

One thing the data sheet doesn't make very clear is that you'll need some ~10 ohm resistors between the driver chip and the MOSFET gates (gate resistors). Keeps the peak drive currents to below what the chip is rated for (1.25A). Also stops resonance in the drive lines and the like but you don't really need to worry about that; just fit some 10 ohm gate resistors and you'll be fine :L