Counting the Number of Table Rows

You can count the number of table rows by placing a number field in a table and summarizing the number using the SUM function in the Calculated field.
Place a number field in the table, and click the setting icon Gear icon, and then click Settings.

Enter a string of your choice for the field name and the field code, and specify '1' as the default value.
In this example, enter "Count" for the filed name and the field code.

Place a calculation field outside of the table, and click the setting icon Gear icon, and then click Settings.

Enter a string of your choice for the field name, specify "SUM(Count)" as the formula, and save the settings.

Now, the number of table rows is calculated.