The CloudAnswers ReportSender app does not impose size limits on your reports being sent, but the program is run on the Salesforce platform so it is governed by the following platform limits that keep the system stable for everyone.
5000 recipients per day
Based on Salesforce's general email limits. This is across all emails sent through your Salesforce org but can affect Report Sender.
12MB file size
This is the maximum amount of heap space Salesforce will allocate to us for file processing. See Execution Governor Limits.
2 Minute Report Processing Time
This is the maximum amount of time Salesforce will let the code wait for the reporting API to respond with the report data.
5 Active Batch Classes at a Time
This limit is not very common but if your org has a lot of batch jobs that run regularly your reports might not always go out exactly on the hour since Salesforce will only process 5 jobs at one time. See the line on "Maximum number of batch Apex jobs queued or active concurrently."