The answer is still the same. A negative texture scale flips the image along the X or Y axis. The panel on the left of the above image is the GLOBAL setting for the selected texture (in this case, t26lava0). By setting its X scale to 0.01 then when it is applied to any object or surface, it is scaled to 0.01 by default. Changing this number does not affect any already applied textures, only ones applied from then on.
The panel to the right gives the same options and a few additional ones as well. If you notice, the ALL box is not checked. This means that the numbers you enter here are affecting only ONE surface and not ALL surfaces of a selected object. In the case of the image above, it would be surface #3. The panel is telling you that the texture applied to surface #3 is scaled -1.00 along its X axis, and 1.00 along its Y.
Well, thanks for providing additional usefull information. My question actually was, if it is possible to set GLOBAL texture scale below zero. Since, as image demonstrates, it is possible to set LOCAL texture scale to anything from -10000 to 10000 while GLOBAL texture scale gets capped into 0.01 .. 100 range.
