Venn diagram illustrating the intersection of three sets: Red, Yellow, and Blue.

Based on the Venn diagram provided, the task is to find the total number of elements in the universal set (indicated by the symbol $\xi$). To do this, we sum the numbers in all distinct regions of the diagram.

1. Inside the Red circle only: 2
2. Inside the Red and Yellow overlap (not Blue): 5
3. Inside the Yellow circle only: 6
4. Inside the Red and Blue overlap (not Yellow): 2
5. Inside all three circles (center): 3
6. Inside the Yellow and Blue overlap (not Red): 2
7. Inside the Blue circle only: 4
8. Outside all circles: 4

Total = $2 + 5 + 6 + 2 + 3 + 2 + 4 + 4$
Total = $28$

Final Answer:
28