Why this code is not right statically in ggplot to get percentage in y-axis?

Question

I have this data, and I want to get percentage in y-axis.

structure(list(sb_1 = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 
2L, 2L, 2L, 2L, 2L), .Label = c("