Count Smaller Numbers - Read Statement

Given an integer array nums, return an array counts where counts[i] is the number of smaller elements to the right of nums[i].

Example: For [5,2,6,1], output is [2,1,1,0]. To the right of $5$ there are $2$ smaller elements ($2$ and $1$). To the right of $2$ there is $1$ smaller ($1$).