Analog Input Pins current rating?

Hi, I am a EE student new to microcontrollers. I started work on a project using Arduino mega 2560. I have a question concerning the analog input pins. I search the web trying to find what the Analog input pins current rate at "min to max current rateing"; however, it seems that I can't find any info on it. I found some specs as follows

Microcontroller ATmega2560 Operating Voltage 5V Input Voltage (recommended) 7-12V Input Voltage (limits) 6-20V Digital I/O Pins 54 (of which 14 provide PWM output) Analog Input Pins 16 DC Current per I/O Pin 40 mA DC Current for 3.3V Pin 50 mA Flash Memory 256 KB of which 8 KB used by bootloader SRAM 8 KB EEPROM 4 KB Clock Speed 16 MHz

I am confuse at what these spec all means. Is the DC current per I/O Pin 40 mA for Digital I/O only, or is it for analog and digital?

Thank you.

The input resistance of the analog inputs is 100 MOhm (from Table 31-11). That means at an input of Vcc (5V) your input current is 0.00000005 A (0.05 microamps). Does that help?

Analog pins can be used as digital outputs if you want - same specs as other pins.

The input current is effectively zero(*) as analog inputs (or digital inputs) unless the built-in pull-ups are enabled.

(*) Typically pA, at room temperature. The datasheet worst-case figure is for 85 or 125 deg C when leakage currents are far higher.

Thank you guys !