The Assignar Mobile App is very efficient in its data use.
When you first open the app, it will download about 1-2 MB of data (that's about the same as when you open the homepage of a popular news website, like the Sydney Morning Herald, or the New York Times).
As you continue to use the mobile app, you will generally consume very little additional data. There are only a few activities that will consume additional data, which include:
Uploading photos (most photos taken on a modern smartphone are 3-4 MB in size).
Viewing documents (these are often less than 1 MB in size)
For most users, a normal day's use of the mobile app will consume less than 20 MB of data. That's very low, compared to for example, an hour browsing Facebook, which can consume 200 MB or more of data.