After downloading, there are some ways to view the offline maps:
You can view downloaded offline map byMap Viewer, and you can zoom out or zoom in the offline map.
Output the offline map as BMP,JPG,TIFF file.
It can even export all tiles to a sqlite database with MBtiles format, then you use the sqlite db on some Android or iOS apps, such as MapBox, RMaps, Oruxmaps, etc.
When you created a mbtiles file, you can view the mbtiles file with MBTiles Viewer.
If you want to make a offline map of your city by yourself, it is very useful for you