The golden rule for bedside tables is keeping the top surface between 5 and 10...

https://wiki-book.win/index.php/Finding_the_Perfect_Fit:_Matching_Your_Mattress_Height_to_a_60%E2%80%9363_cm_Nightstand

The golden rule for bedside tables is keeping the top surface between 5 and 10 centimetres below your mattress top. This makes reaching for your phone or a glass of water feel natural rather than a stretch