For the perfect setup, aim for your bedside table to sit roughly 5-10 cm below...

https://fionafreshmaids.com/the-ultimate-guide-choosing-the-perfect-bedside-table-height-for-a-65-cm-mattress/

For the perfect setup, aim for your bedside table to sit roughly 5-10 cm below the top of your mattress. This makes reaching for your phone or a glass of water comfortable rather than a stretch