Right and Wrong Way to Cut Rafter Birdsmouth?

Hi All,

Currently having an extension built and we're having a debate about the birdsmouth cuts on the roof rafters. Which side of the wall plate does the plumb cut go?
Is there a right and wrong way round to cut a birdsmouth on a roof rafter?

The roof is an abutment to existing house at 15 degrees. No ceiling rafters. To be felted, battened and tiled with double pantiles.

Pics attached of each way for clarification

Many thanks for any advice.

 

Thanks Phil