How much current can this 74HC245 handle on each output pin?
The clamping currents are currents that will flow if you apply a voltage to the input or output voltage below ground or above the supply voltage, see the conditions: Vi &lt; -0.5V or Vi > Vcc + 0.5V

There are ESD protection diodes on all inputs and outputs, on each pin there is a diode to GND and one to Vcc. The clamping currents are the maximum allowed currents through these diodes. Normally you would/should not apply voltages above or below the supply and GND rails. But if you do, do not exeed these limits.

The maximum current flowing in to / out of an output pin may not exeed 35 mA.
The total supply current (which is also the sum of all currents supplied by outputs) should not be more than 70 mA.