What does L mean?

the "L" after a number denotes that is of class "integer" and not "numeric"

#> [1] "integer"
#> [1] "numeric"

Created on 2021-12-10 by the reprex package (v2.0.1)

Also, I haven't manually written the "L"s, that part of the code comes from the sample data (in a copy/paste friendly format). That format is usually produced by the use of the dput() or datapasta::df_paste() functions.

Read this reprex guide to better understand the concept