Sum not giving correct total

Occasional Visitor
HP Pavillion using Windows 10 and excel 2019 (I think-unsure how to check). My car provides a record of trips and mileage which when imported is provided on a CSV spreadsheet. I then Save As to an Excel spreadsheet.

When using the sum function to total the miles driven in a day the total is 1 less than the correct total. There is an error exclamation drop down menu but even though I check all the options, I cannot find the error. If I total adding each figure (using = and +) then the correct total is usually given. The only change I make to the figures is to reduce decimal point and round up or round down the miles for each trip. Anybody know how to overcome this?
Thanks
1 Reply

@DaddioRangie 

If you round the intermediate results, you're bound to get discrepancies:

 

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