I have the following in a spreadsheet for working out time work. Everything
adds up into little columns, however when this entry is put in, it produces a
strange result in the over-time column - I know this entry should read as 0,
but for some reason states that it is and exponential value of -15.
Description or Formula in []

27/08/2008
Cell
F83 Start Time 0630 [Start Time - Just a time entry]
F84 Start Lunch 1230 [Start Lunch - Just a time entry]
F85 Finish Lunch 1300 [Finish Lunch - Just a time entry]
F86 Finish Work 1500 [Finish Work - Just a time entry]
F87 Hours Worked 8
[=((F86-F83+(F86<F83))-(F85-F84+(F85<F84)))*24]
F88 Hours Over Time 1.77636E-15 [=MAX(0,F87-$Z$9)] [$Z$9 is a cell stating
that normal working hours are 8]

Any other times are displayed correctly, for example start at 0630, lunch at
1200 till 1230 and finish work at 1500 produces the result of 8 hours worked
and 0 hours over time.

The formula and what not is a result of looking through here and also some
other related websites. Basically i'm after the reason why it displays
1.77636E-15 INSTEAD of 0 for the over time ONLY when the lunch period or 1230
till 1300 is entered on an 8 hour day.