Hello, I hope this should be fairly simple, most of this is just me
looking to understand how a certain process works.

I have a primary NS where I add in new domains, delete old ones, and
of course, update existing ones. My colocation provider has several
NS's, but I only use one as a secondary, and only list one as a
secondary in my NS records.

For example:

The part I am not entirely getting, is my colo provider has

And probably others

I set in named.conf
allow-transfer { ns0.colo.com; };
* I use an IP, just trying to make this more clear in example

So their ns0.colo.com pulls the zone data from my ns.me.com, however,
the authoritative servers are ns.me.com and ns1.colo.com.

I am guessing, the colo starts with ns0.colo.com, and each of the ns1
through ns3 are slaves.

What determines to them, when the ns1.colo.com, through ns3.colo.com
will pick up on the new data in ns0.colo.com?

When I make a change, it seems to take a very long time for
ns1.colo.com to pick it up, but I can see that ns0.colo.com has it. I
send in the notify, and ns0.colo.com grabs relatively quickly. The
trouble I have, is that their secondary does not seem to get the new
data for far too long.

I tend to think it is a configuration issue on their end, but it
brings me to wonder what configuration I would change. I provide a
secondary for a few friends, many thousands of domains, but I have no
idea how, if I wanted to, I would change the speed in which I pick up
new data from their primary, if they did not send a notify. I suppose
there are also options to enable and disable notify, which I can not
seem to find, and time intervals that can be set when notify commands
are not sent.

Thank you.