While using mfuzz for gene expression analysis i'm stuck at one thing regarding fold change-

1.) I calculated log2 (using R & manually)  and then standardisation manually using (x-mean)/sd taking input of x from log2. Standardisation result done by R is different with respect to one done manually. Manually done result shows two to three protein values above 2(between 2-2.5).But in R standardisation result shows different values which are right according to the mfuzz.plot fold change.Manually done values(few) are beyond fold change.

        So i am concerned about those values. Just want to know the calculation behind it in R ?