# Cable tray width selection as per NEC 392

I would like to ask if anyone know what is the meaning of the letter b used in the formula in the table 392.22 National electrical code 2017 article 392, pic (attached)

• It means that there is a footnote labeled (b) and that footnote applies to those data values. – Elliot Alderson Apr 17 '20 at 20:50
• Do you mean that b is not a part of the equation? Thanks alot for your reply – Aisha Apr 18 '20 at 3:30
• That's right...it's not a mathematical symbol. Look at the heading labeled Column2$^a$...there is a footnote (a) somewhere that applies to the whole column. – Elliot Alderson Apr 18 '20 at 12:13