I check the HS CL650 and line selecting DELETE into the FUEL USED line of the FLIGHT LOG page will not reset the fuel used to zero. I'm 95% certain that this is not correct behavior because it has worked in the DA2000 (PL4 & FMS 6000), the CL300 (PL21 & FMS 5000) and CL350 (PL21 Enhanced & FMS 6200). Still, Bombardier might have asked Collins to set this up differently in the CL650.
I filed it over on the Support page.
Rich