Comprehensive study of high-quality monolayer graphene samples grown by thermal destruction of the Si-face of the 4H-SiC substrate was carried out. Analysis of the data obtained by Raman spectroscopy and angle-resolved photoemission spectroscopy suggest the need to use the Fermi velocity in the graphene layer under study to obtain a correct estimate of the electron concentration and strain values using Raman data. This statement is valid not only for graphene on the SiC substrate, but for graphene on any other substrate as well, since the Fermi velocity in graphene depends on the dielectric constant of the substrate.