Google Voice is not simply a free telephone company for use on an OBi device. It is a full-function inbound call forwarding and message management system.
When someone calls your inbound Google Voice telephone number, GV then forwards that call to all of your selected forwarding destinations, simultaneously. OBi devices are just another forwarding destination, like a land line or mobile telephone number. OBi devices act as Google Chat clients. To control which destinations ring, or don't ring, add or remove the check marks to the left of each destination, on this page:
https://www.google.com/voice/redirection/voice#phonesGoogle Voice does not support sequential forwarding (hunt groups). It rings all destinations at the same time. You can, however set calling schedules. For example, ring forwarding destination A during these hours; ring forwarding destination B during those hours.
You cannot control the number of rings.