When you uploaded you did not set an upload value so the Sw's default mm was used. So SW's printed the dimensions in mm. 7mm =..275 . Attach a simple test model in a post in lwo. I should be able to tell at a glance the workflow you need to get it ready to print. That odd result of your scaling by 1000 is worrisome.
If you ever upload one of the file formats that do not support scene data, you have to determine the true dimensions in basic units of the model. Netfabb is good for determining this, as Paul mentioned. Besides stl, it can open .obj files also.What Netfabb does is display model dimensions in basic units, besides other uses.
Here is a recent problem posted here, similar to yours posted similar to your problem.
A friend made a ring using scene data in mm . Wanted the outer diameter be 2.3cm(23mm) . So with all the measurements correct, he uploaded as a stl
set units to mm at SW. He never looked at the model's diameter dimension in basic , which was 2.3. So SW tried to print it at 2.3mm in diameter. Phail.
Several formats ignore scene data . The meshes basic unit dimensions are stored in the file which when you upload , you have to set the length of the basic unit for to get it printed the required size. bu 4x5x6 uploaded at Inches would result in a Inch 4 x 5 6 model getting printed.
In the case above, he fixed it by scaling the object by 10, getting a diameter of 23. Setting at upload the units to mm, result was a 23mm diameter ring which is the end result he wanted.