If you enter or edit a calculation via the ribbon command Mailings | Field 
| Calculation, TextMaker automatically updates all other calculations in the document as soon as you confirm with OK.
In certain situations, however, calculations may show "outdated" results. If, for example, you copy from another document a section of text containing variables that also occur in the current document, TextMaker will inevitably display incorrect results on the screen.
The ribbon command Mailings | Update fields 
is provided for such cases (alternatively: keyboard command F9). If you choose this command, TextMaker updates the screen display of all calculations and fields in the document.
Note: This command is only necessary in the above cases to update the display of calculations on the screen. Before printing a document, TextMaker automatically updates all calculations and fields. TextMaker thus ensures that you will never print a document with results that are out of date.