Error in if function

Error in if function

I am trying to make a simple if function, but apparently something I miss as I get error when saving

if (input.PF_Deviation < 24)
{
input.Delay_Status = On Time;
}

PF_Deviation is a formula field subtracting two time stamps, hence the the result should be that Delay_Status (drop down) should read On Time when less then 24 hrs.

Any tips?