Nodes are (index) rows in non-leaf pages (page=8KB). In fact, the number of non-leaf pages is very few compared to number of leaf pages. So few, that the number of non-leaf pages is negligible.

Let's make rough estimation for 10M rows:

If leaf page fits 200 data rows on average, we have 10 000 000 / 200 = 50 000 leaf pages. If each non-leaf page fits 400 index records (each index record points to a PAGE of lower level), at the first level above leaf level we need 50 000 / 400 = 125 pages. The next level up will fit all 125 rows in one page.

So, for 10M rows you would have just 2 levels deep index, with 50 000 leaf and 125+1 non-leaf pages.

Number of non-leaf pages is much less than 1% of leaf pages, close to 0.2%. That's why indexes are very efficient and non-leaf pages are often cached in buffer pool.

Just to have a better picture on ratios.