With 10 jobs scheduled and no pictures captured or signatures collected the average data usage is up to 1MB per day. Signature is about 0.02MB. Pictures are what uses most of the data. A single picture is 0.3MB on average.
To put this in example: A technician who had 10 jobs assigned, collected 10 signatures, and took 100 photos used around 30MB of data. He had the same routine five days a week for four weeks and his total data used for the month was 600MB. He had a 2GB plan and 1.4GB was left to use for browsing and streaming music or videos.