How often does feedburner check original url ?

[Davide]

Hi, 

I have an RSS feed generated from a google apps script project and I used the deployed app link in feedburner as the original feed to create a proxy link.

But I don't understand some things though. In my project I have set it to run every 30 minutes and it works smoothly (they are the events of type Time-Driven underlined in red), but I also see that I have the events that run the app through the deployment link, therefore feedburner (type Web App underlined in blue). So:

1) How often does feedburner call back to the link it was given? From my execution data they appear to be random.

2) Furthermore, the executions produced by feedburner do not have logs unlike those produced directly by the project (red and blue arrows), why?