Probably depends on the chart maker, Cabrini.
Following quote from LIDO, do not have Jeppesen definitions available.
1.6.2.11.1.8. Minimum Grid Altitude (MGA)
The MGA represents the lowest safe altitude which can be flown off-track. The MGA is calculated by rounding up the elevation of the highest obstruction within the respective grid area to the next 100ft and adding an increment of
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1000ft for terrain or obstructions up to 6000ft; or
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2000ft for terrain or obstructions above 6000ft.
Example: ELEV of highest obstruction: 6345ft; rounded up = 6400ft + 2000ft buffer = 8400ft MGA
MGA is shown in hundreds of feet. The lowest indicated MGA is 2000ft. This value is also provided for terrain and obstacles that would result in an MGA below 2000ft. An exception is over water areas where the MGA can be omitted.