Hi Michael,
For your requirement , you need to define "10 %" of your targeting audience while defining the waves as below:

Also, you can always check the audit tab of the delivery to verify if your count in the waves is as expected :
Below is one such example:

Once the deliveries are sent out , you can pause/stop them before the next set of wave is executed.
But to start over again and send deliveries to the remaining audience, you got to exclude the one's already sent out in your workflow.
Hope this helps.
Regards,
Anita