I observe the same - on Garmin's maps each tile gets SRT and MDR get its
own SRT too. My general assumption is that GPS sorts subfiles by name,
so 12345678.SRT is used only for 12345678.LBL. If there is 00001234.MDR
then it can use only 00001234.SRT. If there is xxxx.SRT that doesn't fit
any LBL or MDR then it is probably ignored.
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