Numbers issue - not good!

I have been using the Numbers App for many years, without having any problems - I thought. I have to say that when Apple started migrating the App to look and function like the version on IOS, I for one did not like the interface. But hey **, I got used to it.
I use a running Numbers spreadsheet to monitor the spending on my credit card, and when the bill arrives, I reconcile the two.
My new bill didn't tally up. I went through all the columns and couldn't find the problem.
Then I copied the column of individual transactions and pasted it into a new Numbers spreadsheet. Same answer. It wouldn't add up. Proved that by adding it up on a calculator.
So I then pasted that same column into MS Excel, and low an behold it all added up.
It appears that numbers was ignoring 1 of the cells. I still don't know why, but guess what, I don't trust Numbers any longer, and will now use Excel.
Some people have said that Apple's quality has gone downhill since Mr Jobs passed away. I think I would agree. I have other issues with their Safari browser, which simply doesn't work as it did some years ago. Now use Chrome.
I know it's a bit of a rant, but if you use Numbers as part of your business, Be careful!

Mac Mini 2012 i7 16Gig Ram running Yosemite (Up to date)

Thanks for the heads up neilf. I don't even know how to use Numbers correctly, so it won't bother me, but I wish I did, so I could run some tests, and then send bug report. All I know is it works with Formulae's but I'm not even sure how you go about making one of them up . . . . . Hope it helps others.