Why do you state that you are using inactive accounts?
Inviting dozens of thousands of people to the group needs to be done via help of our inactive accounts. Each of them adds number of real people to your group and can stay in your group or leave right away after the invitation is done.
It is up to you to choose, if you wish to keep those inactive members for the number sake, however there is a small risk associated with such decision - Telegram stuff may flag such users and delete them. After such deletion, the users will appear in your group members list as "Deleted Account" which does not look really good.