It's in the Altitude/Minimum Altitude data field:
5.30 Altitude/Minimum Altitude
Definition/Description: The Altitude/Minimum Altitude field indicates
the reference altitude associated with (1) Enroute Airways (MEA, MFA
or other minimum altitudes as defined by source), (2) holding pattern
path of Holding Pattern record, (3) altitudes at fixes ...
As the name suggests, MEA is coded for enroute segments lik ethe airways (ARINC permits this). In so far as Instrument Approaches are concerned, the templates takes into account vertical clearances in Primary and secondary areas and then arrives at safe heights at each segment. Geometry of primary and secondary areas and the clearance therein depends on ...