I. Enter the circled number.
1. Position the cursor where you want to insert the upper corner marker;
2. click insert-> symbol-> other symbols, as shown in figure;
3. The symbol dialog box pops up, and you can insert the symbol as shown in the figure.
Second, set it to superscript.
1, select the circled number;
2. Click the superscript button on the Start tab (or press Ctrl+Shift+= key combination), as shown in the figure.