The terms $2110,\frac{n}{30}$ mean

the buyer receives a $2\%$ discount if payment is made within $10$ days with the full payment due in $30$ days

full payment is due in $30$ days and a $2\%$ penalty will be charged every $10$ days after the due date

full payment is due in $10$ days and any payment after $30$ days will be assessed a $2\%$ penalty

the buyer receives a $2\%$ discount if payment is made within $30$ days