Yup, you will lose data. What it's doing is Going into SETTINGS -> GENERAL -> ERASE ALL CONTENT AND SETTINGS. (which i already before buy your product.) And that's it, you can basically do what the do without their help.
IT is a scam software they only charge you 20 USD and it's not going to solve or fix anything, especially IOS restore issues. just use iTunes or anything else but this one!