the IDs of the layers for a multi layer map are stored in the table wp_leafletmapsmarker_layers, row multi_layer_map_list. This field is varchar(255) - didnt set it higher as a higher memory means more RAM usage...
changing would be easy:
1. make a backup of your tables
2. execute this SQL query via phpmyadmin:
ALTER TABLE 'wp_leafletmapsmarker_layers' CHANGE 'multi_layer_map_list' 'multi_layer_map_list' VARCHAR( 1000 ) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL
3. edit /inc/install-and-updates.php and set line 88 to
multi_layer_map_list varchar(1000) DEFAULT NULL,
updating to a newer version would be harder though: as I dont plan to change this datatype, you would have to download the zip package of a new version manually and repeat step 3 before manually updating to the new version by uploading the files via FTP.
Automatic update would set back the datatype to varchar(255) and thus eventually cut off values which were larger than this.