Cofused about number of simultanous calls

After reading several posts I see anywhere from one to five simultaneous calls with a single phone number. If I have5 extensions how any outbound and inbound simultaneous calls can be accommodated?

If you have 5 extensions, you can have up to 5 concurrent conversations at a time. I would like others to concur though.

Phone extensions

Each phone extension can handle simultaneous incoming and outgoing calls with incoming calls rolling over to voice mail. Depending on how large your business is, you can purchase additional extensions for only $9.99 a month, including virtual and conference extensions.

If you have 5 physical extensions, you could have 5 conversations with another 5 callers on hold.

The virtual receptionist and virtual fax extensions have the ability to handle many more simultaneous callers so that callers to these extensions won’t ever hear a busy signal.