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

https://city-wiki.win/index.php/Bedside_Table_Height_for_a_75_cm_Mattress_Top:_The_Ultimate_Guide

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