I downloaded a raster image from USGS for a part of Malaysia. I opened it by QGIS and ArcGIS Desktop as shown in the attached photo. The first problem is that some values are in a negative and the second is the elevation range in QGIS is different compared with ArcGIS Desktop.
In both software, the initial data range is just an estimate, which can easily be manipulated. For instance, should you display several DEM side by side, you will likely want to use a common range so that a given color has the same meaning across the map.
To get the exact values, in ArcMap you can go to
Data Management / Raster / Raster Properties / Calculate Statistics. In QGIS, go to
style / load min/max values and select
min/max with Actual(slower) accuracy