'Data' refers to the data you are using within Sigma to bill your Tenants.
This can be the Accounts data (Utility Bills) or Metering data (Half hourly data or manual meter readings).
This page will link you to areas within the Help Centre which will help you manage your data:
Accounts Data
Metering Data
How to manual enter Meter Readings
How to import Half Hourly data
How to automatically import Half Hourly data