RINF is a long/short spread ETF. This means it give you positive exposure to one asset and negative exposure to another. Because the assets are similar to each other, the overall risk of the total exposure is relatively low. Therefore it makes sense to lever up, which is what they have done. For every dollar you put in, the ETF takes a long position of multiple dollars and a short position of around the same amount. You have no overall exposure to interest rates if they do it right, but you have a magnified exposure to the difference between real and nominal interest rates (i.e., changes in expected inflation).
The actual assets are TIPS and swaps, but you can imagine doing something similar. Say you want to create a Visa/Mastercard long/short ETF. For every dollar people give you, you buy 10 dollars of Visa and short 10 dollars worth of Mastercard. It's a highly levered but nevertheless reasonable portfolio with only moderate risk because the two tend to move together.
In general, it's not unusual for a portfolio to have greater than 100% total weight. That's just another way of saying the portfolio is levered.