How to read the electrical characteristics

Hardware Arduino Due
1

Hello,
in the "simple audio player thread" a user speaks of 15 mA max. I looked up the datasheet and this is where I need some explanation. On page 1389 there are the "Absolute Maximum Ratings". I think the Due is in a LQFP (how many leads btw?), more importantly there are about 100 mA specified for all I/O lines. On page 1391 however there are also maximum ratings but they don't excel 24 mA. Furthermore the pins are splitted in groups, what's the reason for that and what does "Relaxed Mode" mean? To page 1421: Do I get it right, when saying that "Current Consumption" does not mean the current that is available on the pin?
The actual "hardware problem" what got me thinking is, that I hooked up some standard LEDs that, require about 20 mA and I'm afraid to hurt my Due by not being capable of reading the datasheet in the right way. I hope one can help me with that.

Greetings
decrux

2

more importantly there are about 100 mA specified for all I/O lines.

Add them all up and they must not exceed 100mA.

the pins are splitted in groups, what's the reason for that

Groups have their own limits when it comes to output current.

however there are also maximum ratings but they don't excel 24 mA

These are limits where damage will occur.
Keeping the current below 15mA will be safe.

that I hooked up some standard LEDs that, require about 20 mA

Don't this is not a 'normal' arduino it hasn't got the current capacity to drive much directly.