What quantity of scallions should be included in this recipe?

Here is the recipe from the author's blog: thehappyfoodie.co.uk/recipes/one-pan-steam-roasted-salmon-and-broccoli-with-lime-ginger-garlic-and-chilli . She calls for 2 spring onions. I think you can be fairly flexible, however, and use 3 or 4 scallions if you wanted.