You can see the contract specs here https://www.bitmex.com/app/contract/ETHU... and find more information here https://blog.bitmex.com/why-quanto/
My advice is always to make sure you fully understand a derivative product before you trade it, however many of us may not have the acumen to actually understand how a quanto swap works. Nevertheless, we have to be aware that the value in USD of each contract depends on the price of Ethereum and also the price of Bitcoin at each point in time.
This tool will show you the value of a single ETHUSD contract in USD, but it solely for indicative purposes only. Your trade, your risk. I do not ask for any donations from your gains and I am not liable for any of your losses.
Source code is provided.
Note in the example image that the price of ETHUSD is plotted on a logarithmic scale but the indicative contract value is linear.