What is srv_id 0 zero?

[chadrockey]

Looks like all of our servers (peripherals) start with srv_id 1.

What is srv_id zero?

python-bluezero/bluezero/peripheral.py

Line 35 in 2b0aba8

:param srv_id: integer between 0 & 9999 as unique reference

[ukBaz]

Anything that is created and put on the D-Bus needs to have a unique that to identify it. The path of the service on the D-Bus needs to be made unique.
Which is done here by using the srv_id that is passed in to the peripheral.

python-bluezero/bluezero/localGATT.py

Line 115 in 2b0aba8

self.path = self.PATH_BASE + str('{0:04d}'.format(service_id))

If all your paths are having 1 in them then I'm guessing that is because you are setting it to 1.
The value doesn't matter as long as different paths have different values. You can create random numbers if you want.