it means bitwise shift left.

if $h = 1 and $c = 1 then $i = 2

if $h = 1 and $c = 2 then $i = 4

if $h = 3 and $c = 1 then $i = 6

if $h = 3 and $c = 2 then $i = 12

etc...

if $h = 1 and $c = 1 then $i = 2

if $h = 1 and $c = 2 then $i = 4

if $h = 3 and $c = 1 then $i = 6

if $h = 3 and $c = 2 then $i = 12

etc...