Retail Marketing: What does "sales in volume" represent on a weighted-numeric distribution chart?

Greetings,

I was wondering if you could help me by clarifying a retail measurement that would enable me to conduct a correct reading of a market report. Namely, on the chart that portrays a set of parameters that include weighted stock/out-of-stock, numeric distribution and sales in volume, categorized by various distribution channels - what might the sales in volume represent if its expressed in percentages?

Logically, I would assume that this variable accounts for the percentage of goods sold through these channels but what befuddles me is that this percentage appears to be very small (~5%) in contrast to the actual sales that this brand achieves in the given period of time.

I would appreciate if you would provide me with some brief explanation as to how to read this data without misinterpreting it.

Thank you for your time,

Kind Regards,
Matija Pavlovic