You can use expression form in string_dynamics. A dynamic string is a string that can be referenced from regular strings, but will recalculate every time referenced.
I purposefully chose not to document this in Adventuron Classroom for fear of putting beginners off.
BEGINNERS : Don't be put off please :-)
start_at = village
locations {
village : location "You are in the village. {linger_desc}" ;
}
strings {
linger_desc : string_dynamic {(
"You have been hanging around for " +
linger () +
" turns."
)}
}