Column Width

Hello,

am moving from column-count css to this code : Codepen

I use to have
max-width: 501px : 1 Column
min-width: 502px to max-width: 890px : 2 columns
min-width: 891px to max-width: 1200px : 3 Columns
min-width: 1201px : 4 Columns

with Max column width of 400px

How can I adjust the codepen to match the above ? P.S. Am a bit lost with the fraction.