The document explains how to identify the place value of underlined digits in multi-digit numbers. It provides an example of finding the value of each digit in the number 572,835 by multiplying the digit by its place value. The first underlined digit in 56,345 has a value of 5,000 since it is in the ten thousands place. The underlined digit in 12,678 has a value of 600 as it is in the hundreds place. The underlined digit in 3,490 has a value of 300 since it is in the hundreds place.