page size for A4 paper changed

I have been working on a spreadsheet which has columns of various widths & rows of various heights, designed to fill an A4 page for printing & have done so several times without a problem. However, when I opened the spreadsheet a few days ago, each page now only fills about 2/3 of the width & half of the length of an A4 page. It seems to think that a centimetre is a lot smaller than it actually is, and needs columns adding up to over 27cm to fill the width of an A4 sheet which is really only 21cm wide. I am sure I did something wrong on a setting somewhere to cause this, but for the life of me I can’t find it! Please help!

UPDATE - I have found the probem - under Format > Page > Sheet > Scale, the Scaling factor had been changed to 66%. I have never changed anything on this sheet before, so I have no idea how it happened, but at least I found the answer to my problem!