In my Google Drive I see when a spreadsheet was modified:How to go about seeing what the modification was?
See last modification in Google Drive/Spreadsheets
google spreadsheets;google drive
Open the spreadsheetNext to the menus should be a link labeled All changes saved in Drive. (This message will be different if GDrive is actively saving the document.If you hover over the link you'll see when the last change wasClick the link to open the change log. You'll get a list of dates on the right side, along with the name of the person who made each change.Click on a date and the changes made by that person will be highlighted using the color of their icon.More information at Google Support: Revision history