How does provider/requester priority work?

[septemberWaves]

While learning to use the mod, I noticed that it's possible to set priority for stations. I have two questions regarding that:
1) Will stations with lower priority numbers be used before ones with higher priority numbers, or vice versa?
2) How do stations interact when providing/requesting the same item if one has a priority set while another does not?

[NotRexButCaesar]

While learning to use the mod, I noticed that it's possible to set priority for stations. I have two questions regarding that:
1) Will stations with lower priority numbers be used before ones with higher priority numbers, or vice versa?

Depot: (ignores Requester & Provider signals)
[…]
Depot Priority (optional) - higher priority will be served first (default=0)

[…]

Requester & Provider:
[…]
requester:
[…]
Request Priority (optional) - higher priority will be served first (default=0)

[…]

provider:
[…]
Provider Priority (optional) - higher priority will be used first (default=0)

2) How do stations interact when providing/requesting the same item if one has a priority set while another does not?

I have an impression that stations with no priority have a priority of zero.