I'm using this formula (below) to add the hrs between 2 time periods (4:30 pm in cell I37 and 8:00 pm in I38, then the formula is in I39) and works almost every time even when the second time goes into the am hours, except in certain instances such as: 4:30 pm to 11pm show as 30.5? But sometimes it shows the correct number, 6.5, does anyone know why this happens? Thanks!

=(IF(I37>I38,I38+1-I37,I38-I37))*24