I think current on the I/O bus is provided by current consumption at 24VDC. Is it true or false?

Dear Friends
I'vesome questions about power supply calculation for IM 153.
In attached document ("IM 153-2 Interface Module.pdf "), there are two unknown item for me.
1. Current consumption at 24V = Max. 0.6A
2. Current on the I/O bus= Max. 1.5A

These aremy questions:
[schnippschnapp]
2. I think current on the I/Obusis provided by current consumption at 24VDC.Is it true or false?
[schnippschnapp]

other questions are splitted to

Is consumption of one IM in rack (with I/O Card) is maximum 0.6A or 1.5A or 2.1A ?.

Is I/O bus voltage 5VDC?.