You may have experienced UC Surface on an Android tablet where it seems to display either larger than seems necessary for the physical screen size (i.e. fewer faders shown, more scrolling necessary), or it displays such that more faders are shown, but everything ends up too small to use comfortably.
How UC Surface displays on any given Android device is based on the device's reported dpi and UC Surface's minimum display/resolution requirements (1024 x 748 minimum logical pixels).
UC Surface has three possible scaling factors, and it makes the decision of what scale factor to use based firstly (but not solely) on the device's reported dpi.
An Android device reports a dpi value (physical pixel density). UC Surface uses that to choose a scaling factor of 1x, 2x or 3x, by dividing the dpi by 160 (which is considered a "normal" resolution an Android device).
So, Scale Factor = dpi / 160
If that factor is at least 2.5, use Factor 3x
If that factor is at least 1.5, use Factor 2x
If that factor is below 1.5, use Factor 1x
(The higher the scaling Factor, the bigger the app is drawn on the screen, i.e. less faders shown)
In other words (resolving the equations): you need
400 dpi for factor 3x (400/160 = 2.5)
240 dpi for factor 2x (240/160 = 1.5)
Less than 240 dpi gives factor 1x (e.g. 200/160 = 1.25, etc.)
But, remember, UC Surface also has a minimum size of 1024 x 748 logical pixels.
Factor 2x means that UC Surface will be displayed at 2x the size. This means that, for instance, the device may report a dpi value high enough for Factor 2x, but UC Surface can only use Factor 2 if the physical pixel resolution is twice the minimum size of UC Surface.
So, even if the dpi is high enough for Factor 2x, if the physical pixel resolution isn't at least twice the minimum, then Factor 2x can't be used, and it will revert to Factor 1x (smaller display size, more faders shown).
This limitation comes from the UI design, where the overall layout is indeed flexible but it also has some minimum limits, as some "static" elements can't be resized, hence the minimum logical pixel display requirement of 1024x748 and how that fits into the Scale Factor determination.
If you want to try to determine how a given Android device will display UC Surface before making a purchase, you should look for the device's stated specs on screen resolution and dpi (sometimes noted as ppi).
For a given scale factor to be used, the dpi must meet the threshold requirements noted above and the screen resolution must also be high enough to support that scale factor based on the UC Surface minimum resolution of 1024 x 748 (i.e. 2x requires at least 2048x1496, and 3x requires at least 3072x2244).