Confused about monthly data usage settings

Working on a template to set monthly data limits. One field allows selection of the monthly limit units (MB or GB). Next field accepts “Monthly Limit (in units as specified above)”. Field after that accepts “Monthly Limit (KB).”
Here is the problem. If I specify the monthly limit units and enter the desired number of units in “Monthly Limit (in units as specified above)” the “Monthly Limit (KB)” autofills with the same value. If I specify 5000 as the monthly limit in MB I end up with one field specifying a limit of 5000MB and the next specifying a monthly limit of 5000KB. The template will not accept unchecking either field or leaving it empty, nor will it accept differing values in the two fields. Which of the two values is actually used by the device, and why am I required to put the same value in both fields?