tyGraph Pages has three date limits that you can control at various levels to optimize the experience of your audience, custom to their situation.
tyGraph Engine
Once you have successfully installed the tyGraph Pages engine we will begin collecting information. This data is collected going forward from the moment the installation is complete. This represents the earliest possible date you will have data.
Application Insights
Each day the engine will store your data up to a maximum of 730 days in application insights. By default this limit is set to 90 days by Azure. So if you are customer deployed consider expanding the limit to 730 days, if you didn't already when you created it in this step.
Related Article: Changing Azure Log Analytics Retention : Support (tygraph.com) 
Power BI
Finally you can control how much data Power BI pulls into the dataset in the Parameters of the Dataset. This allows you to pull in less data if you want to analyze the entirety of of a huge tenant and keep the reports snappy, or if the permissions of the audience does not include a long period of time.
You can change the Power BI dataset limit as shown below:
