Almost certainly scale. More details needed, like the System Units and the actual sizes of the objects in the scene.
And I suggest you read the Help regarding the "unit slider" which will explain why it didn't make any difference.
Max 2016 (SP1/EXT1)
Win7Pro x64 (SP1). i5-3570K @ 4.4GHz, 8Gb Ram, DX11.
nVidia GTX760 (2GB) (Driver 430.86).