@The-Rogue-Blade Your idea is correct but you missed some pairs and also, a<b so pairs with the same numbers are incorrect. When prof. loh drew a line across the chart he did it above the middle, so he excluded all the pairs with the same numbers.
These shouldn't be included️
2: 1,1
3: 1,1
4: 2,2 1,1
5: 2,2 1,1
6: 3,3 2,2 1,1
7: 3,3 2,2 1,1

I really liked the way you did the question and it would be quite useful if I didn't want to draw a graph