$\frac{1}{10},\frac{n}{15}$ is interpreted as:

A$)15\%$ discount if paid within $1$ day

B$)10\%$ cash discount if the amount is paid within $1$ day, the balance is due in $15$ days.

C$)1\%$ cash discount if the amount is paid within $10$ days, the balance is due in $15$ days.

D$)15\%$ discount if paid within $10$ days.