Trending @Accenture; How many marks = how much proficiency, if my competency exam for 50 marks and 50 questions, any idea?

No idea, these proficiency tests seems to be very vague. Don't understand the marking system fully.

For some tests I got a P3+ unexpected.

For some test where I expect a P3 minimum but got p2.

There are no marks provided. You'll only be present with a rating after your assessment. You can however see in which particular area of skill you have scored better against other areas.