Blue triangle says "Duration Units were removed" How to..?

Question

I used a formula (the formula is  =MAX(K21-8, 0)  if that helps) to calculate OT hours worked from a shift. I wanted it to show 0 if none, and the # of hours over 8 if more than 8 were worked. I needed it to show 0 for the total weekly calculations each week and YTD. This works perfectly fine. But it has a blue triangle in the corner and when I hover over it, it says "Duration units were removed". This is also ok, doesn't cause any problems...yet.
I am trying to have another box show total regular hours worked that day. There are some days where employee will work 5 hours, or 7 hours, and others will be 10 hours or 12 hours.
I am using the "IF" formula, trying to say IF(the amount of hours in a particular cell are less than 8, then just copy the same time/number/duration from that particular cell, if not just write 8)
NONE of the several ways I have tried have worked. I am not very numbers friendly..... Dont understand too much.
This is what I am using =IF(K21<8, K21, "8") - but I have also tried with=IF(K21=<8, "K21", "8hrs") and just about every combo possible.
Not only do none of them work, all coming up with a red error, I think I may be able to get them to work if I can 'remove the duration units' like the other cells automatically did.
HELP?

Answer 1

Hi pw,
K21 contains a duration value, from which the formula subtracts a number. Since the number is NOT a duration, and no units are specified for it, Numbers makes an assumption regarding the unit value associate with this number, strips the duration from the value in K21, and presents the result of the subtraction. That result is a number, not a duration, and could be wrong if Numbers made a wrong assumption, hence the warning.
One way to get rid of the warnng triangle (and to ensure that the subtraction result is what you want it to be) is to convert the duration to the equivalent number of hours:
=MAX(DUR2HOURS(K21)-8, 0)
With this conversion, the formula is subtracting a number ( 8 ) from a number ( DUR2HOURS(K21) ), and no warning is generated.
"I am trying to have another box show total regular hours worked that day."
You can pull these out of the total using a similar formula to the one above. Any hours worked, to a maximum of 8, is regular time. Anything over 8 is OT. To determine OT hours, you subtracted 8 from total hours, and used the result if it was greater than zero, and zero if that was greater than the (negative) result. Here's the other side of that:
=MIN(DUR2HOURS(K21),8)
If the number of hours worked that day ( DUR2HOURS(K21) ) is less than 8, then that's the number of regular hours that day. If it's greater than 8, then the number of regular hours worked is 8.
Here's a table showing the results for several durations of work day:
Formulas in C and D as shown above, with B2, etc. replacing K21.
Regards,
Barry