Beginning with PI AF 2015 R2 (2.7.5), PI AF's Unit of Measure (UOM) supports case sensitivity. This means that abbreviation name clashes such as milliwatt and Megawatt can now be expressed as mW and MW respectively. Previous to AF 2015 R2, this could not be done.
Another change occurred beginning with PI AF 2017 R2. By default, when an AF server is installed, UOM case sensitivity is turned off, but starting with AF 2017 R2 (2.9.5), the default is to have UOM case sensitivity turned on. On the other hand, if you are upgrading to AF 2017 R2 from a previous version, then the UOM case sensitivity will be unchanged (i.e.: it will be set to the same value as before the upgrade).
To turn on UOM case sensitivity, execute "AFDiag /ucs" from a command prompt in the %PIHOME64%AF folder (typically C:\Program Files\PIPC\AF). To turn off case sensitivity, execute "AFDiag /ucs-".