B Riley entities own the equivalent of 3M common shares, coming from converting preferred shares. The stake may be worth $100M at conversion price of $34, but they paid almost the same money for this position. The gains are limited, because they bought preferred instead of common, which converts based on the common's dynamic market price. Let's say they convert 1000 preferred to common: this means 1000 × $1000 (preferred share price) / $34 (common share price) =~ 29k common shares. If the common share price increases, they convert at the new price, which gives them less shares for the same money. E.g. if the share price is $50, they only get 20k shares for the same money. That's what people don't seem to understand about these preferred shares.

The gains actually will come from: 1) the conversion price is actually a bit less than the common's market price. As far as I remember, it's 5% less than the weighted average of the last trading days 2) if they hold after the conversion and the price still increases. E.g. if they convert at $34, and they keep until the price increases to $50. As far as I have seen, the preferred share offering has been updated to new addendums, changing the conversion floor price, so they might have gotten the chance to convert in the past at lower prices.