Counting the number of rows in a default table means that as you click '+' when filling out your form, the row automatically shows the row number. This can be solved by placing the formula in the display cell:
=TEXT(ROW(),"#")
or
=TEXT(ROW(),"0")
Alternatively, you might want to have a separate counter display (Table 2) for the number of rows in your default table (Table 1).
To count the number of rows in a separate counter display table, use the formula in the display cell (in Table 2):
=COUNTA(Table1!A:A)
Note: Use a Prefilled table as the display counter