I believe we are all saying the same thing and it's quite understandable. What might be confusing to some is not knowing if examples given are complete or just one scenario.

For example, an incoming PSTN TF call forwarded to out to a PTSN (cell for example) - two charges, correct?

But if an incoming PSTN TF call gets sent to my primary VOIP number, then we would be charged for the incoming PSTN call only, and not for the TF to SIP, similar to a virtual number ringing on the primary - correct?

I think this is what has been confusing about the in/out - PSTN/SIP visual.

Can I assume my two examples are correct or do I need a beating - LOL . . . But seriously, do those two TF scenario's explain two ways we can be charged a little clearer?