Difference between a % lead and points ahead

Baggs

I read this in an article by Katy Balls: "Starmer only requires a 5 per cent lead in the popular vote for a Commons majority. Current polls put him 20 points ahead."

What is not clear to me is how percentage leads and points ahead relate to each other and why KB would use both measures in the same sentence.

Quite often, using different measures e.g. % pay rise and £ pay rise are meant to confuse.

Did Katy Balls actually realise the difference between the two?

I don’t understand how, as we don’t have proportional representation, ‘a 5% lead in the popular vote’ carries meaning.

The current points lead is purely based on people surveyed, which at this point in the GE cycle is equally meaningless.