Upon creating your Superposition contract, its USDC and ILK tokens value are equal – over time the USDC value is decreasing – with a minimal amount, according to the 4,3% APR. This amount serves as an assurance: you can relax, your value is preserved.
Since the market cap of ILK – in correlation to ETH (or other supported currencies) is far less, even a minimal market activity is able to influence its exchange rate significantly. This practically means, that by creating a Superposition you are guaranteed to always have the USDC value, AND you have the potential of realizing gains with your ILK tokens.
The Ether movement serves a purely visual purpose, to show what would have happened if you stayed in ETH instead of opening up a Superposition.
If you feel the market sentiment is going to shift positively during your contract, remember: you can close your Superposition contract any time without any additional costs and get back into Ether!