The meter components for control panels always have scales from 0 to 15. That reflects the fact that they measure redstone signal strength; however, in real life, gauges are usually marked based on the quantity that the user cares about, rather than the internal implementation of the measurement equipment. For example, a real-world fluid tank level sensor might at some point convert the fluid level to an electrical voltage and then measure the voltage, but the corresponding gauge on a control panel would still be marked in litres, not volts. It would be nice if the panel meters could be marked with any range of numbers (or at least any maximum number, with the minimum always being zero) so they would reflect real-world units (for example, a gauge showing fluid level in a tank would have a maximum of 512 instead of 15). Dynamic texture creation might be hard, though, in which case IMO it would even be an improvement to just have a second texture with no numbers at all, rather than incorrect numbers.