Basically, Monthly Record Limit is a counter associated with each Salesforce Username that will count your processed (successful or not) records within a month. This is because even if your record import/delete fails we sent a request to Salesforce and capture the response consuming application resources.
However, if a Task Run fails or gets expired after 2 hours of execution we are not going to count as processed records because you won't be able to see the Salesforce response for each record.
This monthly limit counter is reset the first day of each month.
If you import/export/delete records accidentally our team won't be able to reset this counter manually and you will need to wait until next month or upgrade to a higher dataloader.io plan if you reach the monthly limit for your current plan.
Sometimes you are working on an import/delete task and you get a message that you reach your monthly limit but your file has fewer records that your remaining quota. We would suggest to open the CSV input file using a text editor (i.e. Sublime for Mac or Notepad++ for Windows) and scroll to the bottom of the file. Extra line breaks could be the main reason for this problem and you need to delete them prior to re-run your task (this is not visible from Microsoft Excel).
To view your currently monthly usage follow these steps:
Login to your dataloader.io account;
On the top right of the screen click on your account username button and select settings;
Select Subscription from the menu on the left and you will see your Monthly Record Limit.