Q:

How many 6, 7 and 8 digits could be generated

Suppose we have a number with the following format ($9$ digits):
$$\mathrm{xxxxxxxxx}$$
Now, suppose we have $100,000$ numbers using the left $5$ digits in the above format.

How many 6, 7 and 8 numbers can be generated without any overlap with 5 digits, 6 digits and 7 digits number, using the left 6, 7 and 8 digits of the format?

The remaining numbers of the format could be any thing.
I know that there is $100K$, $1M$, $10M$ and $100M$ numbers can be generated using the left digits. But I don't know about the overlaps between the generated numbers.
An example:
$5$ digit number: 101010000
$6$ digit number: 101010000
We can't recognize the difference of the numbers.

A:

If you have $100,000$ five digit numbers you have all of them, from $00000$ through $99999$.  That means you cannot generate any $6,7,8$ digit numbers without overlap.  For each five digit number you delete from the list, you can add $10$ six digit numbers, or $100$ seven digit numbers, or $1000$ eight digit numbers or some mix of them.

