Dell supplied Windows 10 upgrade disc

When I purchased my Dell xps 8900 with windows 7 a couple of weeks ago i was sold a windows 10 upgrade disc with the package. I was told it was for an upgrade and no current software will be lost. I started looking into doing the upgrade and on the back of the disc wrapper it said to ensure that the BIOS setting is set to UEFI. My BIOS is currently set to legacy. The information i am seeing states that all current software and settings will be lost if i do this and i will be installing the windows 10 "upgrade" from scratch. Also is there any information on the upgrade fom the dell windows 10 disc. The information provided by the website on the wrapper is about "Windows 7 Downgrade systems fail to boot to Windows 10 recovery media". www.dell.com/.../SLN300634