They should never ever be on a map card.
If you where unconcered enough export the data to a Navionics map card. Copy the Matrix folder and paste it to a blank memory card. Then DELETE that folder off of the Navionics card and hope you did not corrupt the card. The Navionics card should be LOCKED when it is in your sonar unit.
If you are mistaken that the unit will automatically write the data to a memory, you are wrong. Those are created by the unit and stored in the unit's memory Waypoint Library. The only way to get that data copied from the unit is to intentionally EXPORT it to a blank memory card.
The procedure is with a blank formatted memory card of 32GB or less in one of the card readers--1 GB is plenty:
Go to the Nav menu tab
Down to Waypoints Routes, Tracks and right arrow the 4-way button.
Up arrow the 4- way to Options and right arrow.
Down arrow to Select All and ... then right arrow.
Down arrow to Export and right arrow to begin. Only take a few seconds.