If 72° is used ti represent 4 people. how many people were there altogether?

Is there any possibility that you're looking at a pie-chart and not
sharing it with us ?

Let's see.  If 72° represent 4 people, then each person is (72°/4) = 18° .
But then they would all freeze and get sick. No, that can't be it.  It must
be the other kind of degrees ... the kind in circles and angles.

OK.  If 72° represent 4 people, then each person is (72°/4) = 18° .
Now, if the whole crowd exactly fits into one full circle, how many
could that be ?

Well, there are always 360° in one full circle.  And each person
uses 18° .  So how many times can 18° fit into a full circle ?

       (360°) / (18°)  =  20 times.

So 20 people exactly fit into one whole circle.

Does the question have anything to do with that ?

The line "And I bet I never shall" said by Herbert White gives a hint that something bad will be going to happen in the future. The sentence is an example of foreshadowing where the event which would going to happen in the future are hinted priorly.

Explanation:

The first wish that the family wished from the Monkey's paw was to get a sum of two hundred pounds. By that money, they could repay the debts of the house. After wishing, the very next day Herbert goes out to work where he meets with a machine accident. The family receives a sum of two hundred pounds as compensatory money from the company. The line said by Herbert "And I bet I never shall" is the evidence that the money which the family would receive as a wish from the monkey's paw would never be seen by him. This was an indication that Herbert would be no longer alive to witness the sum of the money.