Solutions
-
OxkyGThaib's post in Altitude constraint on the PFD was marked as the answerSee the Down Arrow showing the FCU Target Altitude at the RUNNN point, it strict between FL170 to FL140. That is why the FL160 on Altimeter doesn't showing Magenta because FMCS calculates that you will reach FL160 approaching RUNNN Point which WILL NOT PASSED BEFORE FL170 or AFTER FL140.
Unless you have changed one of the constrain after RUNNN (like SYMON or IRNMN) to AT FL165 OR ABOVE, then you will have Magenta on Altimeter.
Cheers
HaveASafeFlight!