Why the number of sectors does not match and what about the volume?

Question

Hard disks

1 question.
stupid. outdated. CHS

Here is a screenshot from Aomei Assist. Written:
Total sectors 986622.
Cylinders (tracks) 61
Heads 255
Sectors per track 63
1 sector = 512b
count: sectors per track*number of tracks*heads
63*61*255=979965
why???
we consider the volume of the disk:
63*61*255*512/1024**2 in mb = 478.49853515625 it is written that 481.75
where do they go?? why on one line one infa on the other another?

2 question.

Why does the partition start on the next sector after the partition table and only through 1 head?
Why does it end not in the very last address, but leaving a lot of space and what is there?

There, through a bunch of zeros after the last sector of the only section, is exactly this ..
What is it and how did it get there? Where is it documented that this is how it should be?
The section was created as much as possible in volume and filled with zeros.
any ideas

Answer 1

we consider: sectors per track*number of tracks*heads
63*61*255=979965
why???
because for compatibility and therefore it is not obliged to reflect the real value. all modern disks have been using LBA addressing for more than two decades (the same value of physical total sectors).
Why does the partition start on the next sector after the partition table and only through 1 head?
because this implies the MBR standard: the first 63 sectors are reserved for a possible bootloader additional code.