Counting by \(100\)s means going up by 100 each term instead of by \(1\).

Here is usual counting: \[1,2,3,4,\dots\]

Here is counting by \(5\)s: \[100,200,300,400,\dots\]

In regular counting by \(1\)s you can start from any number. Here is counting by \(1\)s starting from \(463.\) \[463,464,465,466,467,468,\dots\]

Here is counting by \(100\)s starting from \(463.\) Each term goes up by \(100.\) \[463,563,663,763,863,963,\dots\] Notice that every terms counts by 1 in the hundreds place. The ones place and the tens place never change.