The uncount() function from tidyr can do this.
library(tidyr)
DF <- data.frame(Size = c(0.6, 1.44, 1.95), Occurence = c(0, 10, 14))
DF
#> Size Occurence
#> 1 0.60 0
#> 2 1.44 10
#> 3 1.95 14
NewDF <- uncount(DF, weights = Occurence)
NewDF
#> Size
#> 1 1.44
#> 2 1.44
#> 3 1.44
#> 4 1.44
#> 5 1.44
#> 6 1.44
#> 7 1.44
#> 8 1.44
#> 9 1.44
#> 10 1.44
#> 11 1.95
#> 12 1.95
#> 13 1.95
#> 14 1.95
#> 15 1.95
#> 16 1.95
#> 17 1.95
#> 18 1.95
#> 19 1.95
#> 20 1.95
#> 21 1.95
#> 22 1.95
#> 23 1.95
#> 24 1.95
Created on 2022-05-02 by the reprex package (v2.0.1)