Question regarding "Beta Hedging lecture 11"

What is the definition of 'dollar-volume' on this website? The traditional definition is 'product of average stock volume and stock price'. In the aforementioned lecture, the author uses code to hedge out the beta by taking a short position of '−βDV, where DV is the total dollar volume of [benchmark].'

However, the code (shown below) uses r_b = [benchmark returns] instead of its 'dollar-volume'

    1. portfolio = -1*beta*r_b + r_a


So, my question is whether benchmark returns and dollar volume are interchangeable terms?

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