You can create as many reports as possible with the Nightwatch logo. However, you can only create reports with a maximum choice of different logos of your own depending on the plan you're subscribed to.
For example, the plan with 1000 keywords allows you to create 15 White Label Reports, which means you can have a maximum choice of 15 different logos in your report. Plan with 6000 keywords enables you to create unlimited white-labeled reports per month.