Most probably you have already noticed that there are two types of limits that you can spend when you generate reports: Report Limits and Free Reports.
Report Limits appear on your account when you purchase Report Packages.
Free Reports come with Starter and Business subscription plans.
In other words, Report Limits and Free Reports are the same thing but they come from different types of purchases.
When you have both Report Limits and Free Reports, by generating new reports you spend Free Reports first. When you are run out of Free Reports the system automatically starts charging you by Report Limits.