I have a very non-technical related question about the report card.

I am looking at this chart:

If I want to measure the unique visitors to Wikimedia projects should I sum up al the categories in this graph or just take the 'world' information?

I'm asking this because 'world' seems to suggest a summation of the other labels. However a sum of all regions does not equal the number under 'world'.

Cheers,

Maarten