Robinhood Monthly Total Platform Assets.
According to Robinhood, Total Platform Assets is defined as "the sum of the fair value of all equities, options, cryptocurrency, futures (including options on futures and swaps, including event contracts), cash held by users in their accounts, net of receivables from users (previously reported as Assets Under Custody), and any such assets managed by RIAs using TradePMR’s platform that are not custodied by Robinhood, as of a stated date or period end on a trade date basis".