DMTech 1019QCB Manual page 73

Security
Unknown sources: Set the device to install applications downloaded from any source.
If you do not select this option, you can install only applications downloaded from Play
Store.
Storage
View memory information for your device and memory card. You can also format the
memory card.
Formatting a memory card will permanently delete all data from the
memory location.
The actual available capacity of the internal memory is less than the
specified capacity because the operating system and default applications
occupy part of the memory.
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