Electronic – Confusing ratings of maximum current sunk/sourced by a pin in PIC24E datasheet

Absolute maximum ratings are there to tell you what is (pretty much) guaranteed to damage your IC if exceeded, they are not recommended for normal use (notice the "at these or above..." in the first clip below)

All decent datasheets will have recommended operating conditions, which are the ones you want to go from rather than the absolute maximum values. For most small micros, 15-20mA is a typical maximum operating condition.

In the datasheet for your uC, it gives a table showing the OH and OL voltages over current, which both range up to 20mA. Note the voltage rise/drop at 20mA and you can see exceeding this will cause the OH and OL levels to go out of spec compatibility wise (example shown for 5V supply - things are different for 3.3V and 1.8V)
For example you can see at 25°C, the output low voltage is at around 0.5V @ 20mA (more with higher temp)
So, I would assume 20mA max for the outputs (at 5V - see other tables for 3.3V and 1.8V). Also take note of the little notes under the tables detailing the guaranteed hi/lo input values and combined current ratings.

Basically decide on your operating conditions (temp, voltage etc) read all the tables carefully and do the math to make sure you keep within specs.

If you are planning on driving some LED displays, either use an appropriately rated driver chip or add some discrete transistors on each pin to drive the LED. Unless you are only using a couple of low current indicator LEDs, this is generally the way to go.

What it means by 6mA at 5v, is that at 6mA, the output voltage level of that output will be fairly close to 5v (or VCC). The more current you source out of an output, the lower that voltage will be. This is called Voltage Droop, or Sag. Same goes for sinking current, with the voltage level rising, so instead of it being 0.0 or 0.1, at 20mA it might be 1v.

Notice that at a VCC of 4.5V, Voh (Voltage Output High), at Ioh (Current output high) -20µA (or -0.02 milliamps, the - indicating sourcing current) the typical is 4.499 volts. While at -6 mA, the typical is 4.3? Your output just lost 0.2v with only 6 mA of current draw. Anything more, and that drop will increase an untested amount. Some datasheets actually have a graph for this. This one does not. So you can draw more than 6mA, up to the max Io output current of 35mA (plus or minus) on a single output, but the voltage level will change to the point where it might not be useful to you. Ex. At 35mA, you might not be able to light an led.