Recipe wording question, help!

My friend and I are making a cake and wonder if the recipe wording is vague. In bold below, when adding the flour, three questions arose:

1. Is the mixer still ON and on low speed while we're adding the flour?
2. Are we still using the whisk attachment for this part?
3. After each flour addition, do we incorporate it completely, or wait to do that until switching to medium speed in the next step?

"In the bowl of a stand mixer fitted with the whisk attachment, beat eggs on medium speed for about 30 seconds, then slowly add sugar until incorporated. Increase speed to medium-high and beat until egg mixture is very thick and glossy, 5 to 7 minutes. Reduce speed to low and slowly mix in melted butter mixture and vanilla. *Add flour mixture in three additions, scraping down bowl as necessary*, then mix on medium speed until fully incorporated, about 30 seconds. Using a rubber spatula, scrape batter into prepared pan and bake until toothpick inserted into center comes out clean, 30 to 35 minutes. Transfer cake to wire rack and let cool 10 minutes."

Thanks guys. I feel like I might be reading too much into it but I want to get it right!

bon appetit