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

https://www.mediafire.com/file/ci4j8luw7hfr284/pdf-67918-84454.pdf/file

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