For the best look and easy access, your bedside table should sit 5-10 cm below...

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

For the best look and easy access, your bedside table should sit 5-10 cm below the top of your mattress. This prevents you from knocking things over while ensuring your book or tea is within comfortable reach