The phrase "several dozen" means there are many items or people, but not an exact number. It generally refers to a quantity between 24 and 36. Full definition
As a child, whenever we went to visit my grandparents, my grandma always had a spread of several dozens of different varieties of homemade goodies. (alidaskitchen.com)
Most of the time, however, there are several hundred amino acids per protein, with several dozen of any particular amino acid. (whfoods.com)
Instead of trying to figure out which companies will perform best, you can use this ETF to invest in several dozen of them. (fool.com)