The golden rule for bedside tables is keeping the top surface within 5 to 10 cm...
https://www.novabookmarks.win/for-a-comfortable-bedroom-your-nightstand-should-sit-level-with-the-top-of
The golden rule for bedside tables is keeping the top surface within 5 to 10 cm below your mattress top. This makes reaching for your phone or a glass of water effortless while you are in bed