Silver Lake's investment wasn't dealt with correctly in the accounts originally. It was initially treated as an equity investment, where they buy shares at a given price and receive any dividends paid to other shareholders. As with any shares, the value can increase or decrease.
We don't pay any dividends, as all spare cash is reinvested in the squad, but Silver Lake's investment was (or has been converted to) preference shares, on which they receive a set amount of interest I believe.
Hopefully, at some point united will go into administration, the share price will collapse completely and Sheikh Mansour will take them over for £1. Then he can take dividends out of them that will make the ones taken by the Glazers look like small change.