OpenstackDashboard problem [devstack]

I have already installed Openstack from devstack . So I still have BIG Question about this Openstack Dashboard though.

1. I'm still confused about amount of VCPU's that provides in Openstack Dashboard. In the quotas tab it was state up to 20 (core) VCPU's, HDD up to 1 TB, and RAM 51200.

This is my case : My PC has 6 core CPU's, HDD 80 GB and 4 GB RAM.

I create custom flavor (e.g : 10 (core) VCPU's, HDD1 30, HDD2 60, RAM 2GB)

And then I run the Images and choose this flavor in 2 instances. If i calculated it : it was 20 VCPU's, 180 GB total HDD, and 4 GB RAM. It worked !! Status Active, Power State Running, but it's really strange if know that my sources only support 6 cores CPU, 80 GB max HDD, and 4 GB RAM. How come it still works ? It's out of my mind, is this Openstack i made just to try the Openstack Dashboard for purpose ? So, I can't run the images i created (ex: Ubuntu) ? Maybe you can help me to explain how it works ?

2. Second things i wanted to ask you why can't I run the Images with flavor xx VCPU's, xx GB HDD, 3/4 GB RAM ??? But, strangely i can run the 2 instances with 2GB RAM each, or 3 Instances with the portion 1GB, 1GB, and 2 GB. Is this bug of Openstack ?? Can you explain me how can that things happen ?

Sorry for my bad English :D
Hope you understand what i mean :(