Everyone stirs natto differently and there is no "correct" way.
It seems like Japanese stir the natto around 30times on average.
The more you stir it, the thicker it becomes.
Rosanjin Kitaoji, the famous Japanese gourmet (OG foodie) said "the more you stir, the better the taste."
On the other hand, some people dislike the thickness and eat it without stirring much. Find your own balance of stir rate and speed for the best tasting Natto.