For the full proposal, please see this forum post.
Fluctuations in the UNI token price means that the accounts for various programs become unbalanced–sometimes at a surplus and other times at a deficit. Since programs are almost always budgeted in terms of dollars, we are looking to top up those balances to ensure liabilities around sustaining elected DAO programs are covered. This temperature check associated with rebalancing is being run separately from the UAC Season 3 renewal vote–the vote will request 42,060 UNI.
Further details on the request and breakdown of budgets can be found at the forum post above.