Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 417.71
Broken: version: 2.80 (sub 74), branch: blender2.7, commit date: 2019-06-09 21:43, hash: rB030c7df19da9
Short description of error
If you're working in Imperial units, typing a metric number (i.e. 10m) into the Dimensions field will not set the object to 10 meters. The scale will be far off. In order to get the scale correct, you have to switch the Unit System back to Metric, then enter your dimensions in metric, then switch back to Imperial.
Exact steps for others to reproduce the error
Start with the default scene
Set the Unit System to Imperial
Select the default Cube
Go to the Numeric (N) panel and set the Dimensions for the X axis to 10m. Then press enter.
The X dimension will go to 52,800'. This is 16093.44 meters, so something is wrong in the math.