What does the hole size and diameter of a via means in Altium? What do they actually represent?
In short/rule of thumb: If you are unsure that your via can carry the current you want, place more vias (more that you might need).
A short answer: Yes, it will able to carry the 500mA (But I think the via will get hot, so place a second via there as well)
The internal of a via:
As you can see current flows on the walls of the via. If you fill the via with copper afterwards, it will be able to carry more current.

taken from here
Via filling example (blue is the copper fill, there is no solder mask (green) on this via so it is easier to be filled by you, the user/engineer):

Taken from here
You can see below, the &quot;finished hole&quot; is your 0.75mm hole and pad size is your diameter (1.35mm).

pic from here
You can calculate here how much current can pass through your via. You need one more information to calculate the current that can pass through the via. This is the Plating Thickness. This is the thickness of the copper on the top, bottom, in the vias and pads of the pcb. The via length is the length of your pcb.