This article explains the difference between the percentage shown on the CrashPlan mobile app and the percentage shown on you My Account page. Your file selection may not be 100% backed up if you receive an email warning that "you haven’t backed up to CrashPlan for over 3 days or more".
Under the hood
My Account and the CrashPlan mobile app display two different reports: Last Connected date and Last Backed Up date.
My Account displays the Last Connected date and percentage. This tells you the last time CrashPlan backed up new data. The backup may not have reached 100%.
The CrashPlan mobile app displays the Last Backed Up date. This is the last time CrashPlan was able to back up your file selection to 100%.