Confused by scale issue when set to 1:1_1

[Bob658]

I have two different models. both have the units set to metres and both have the scale set to 1:1_1. However when the 'Edit Drawing Scales' when you select the 1:1_1 it states at the bottom that '1 paper unit = 1 drawing unit' but in the other model ''1 paper unit = 0.001 drawing unit'. As you can't edit this I'm not sure how it happened. Can anybody shed any light on this.?

[CyberAngel]

How is "1:1_1" different from "1:1"? Is it possible there's a duplicate scale?

[Bob658]

It's not a duplicate scale. As far as I'm aware 1:1_1 is a standard scale and generally that's the only one I use.