Andriod app reading incorrect volts via MCP3008 analogue inputs

I have a Raspberry Pi 3B, a mcp3008 a/d converter. For reference I have ch7 input on the mcp3008 tied to VCC (3.3v). Using IE / laptop the voltage displays correctly at 3.3v, on the android app (Samsung S5) it displays 1.0v.
Ch 6 is tied to earth and reads correctly as 0v on both IE and android app.