It tracks BCOMCLTR:IND as we all know. Low on that thing was $113 when UCO reached $5.98. Currently that one trades at 134.64 - up 19.15% from the lows. So UCO should be up double i.e 38.3%. Guess what today's close of $8.27 - $5.98 = $2.29 gain which is exactly 38.29% of $5.98.
Irony of it, it is a 2x daily trade vehicle but it seldom appears to be doing so. But above Math says over a period from its low to the current price in a month or so, the math is right on.