Beyond that very easy to draw conclusion, the usage of the device types shows an interesting pattern and reveals some insight into user habits when looking at daily usage patterns.
With a different scale on the data volumes the user patterns emerge, these show that user habits are fairly consistent over the hours of the day (despite different value scale).
Using the computer values as a base line for user habits the trend is consistent for all devices over the hours of the day. The mobiles have a quick start with the 7 to 9 time frame which indicates a commuter window.
The lunch dip is present for all devices except for tablets which has a steady increase over the day until the last hour of the day when all devices start to decrease as the users drop into bed.