Leveraged etf on margin difference

On ETF UPRO leverage is 4x of SP500
But broker wants 25% each leverage which makes 4x = half?

So let’s say I have 10k cash
When buying UPRO, I can only use 10k instead of 20k (margin account) due to required maintenance of 25% per 1x ?

Is this correct?
Then effectively this 4X etf is only really a 2X since I couldn’t use margin right?

Please advice. I’m a noob here
Thanks