We perceive a change in the loudness level on a logarithmic scale. For this reason, in professional equipment, signal levels are marked in decibels. Double level change is 6 dB. Where the sound is tuned exclusively by ear, often use a scale in percentages or abstract divisions.
Usually, when using the scale in percent, the maximum level is 100%. Accordingly, the volume range is between 0 and 100%, where 0% is silence. If the position of the regulator in the middle corresponds to 50%, it means that the sound adjustment is linear, not logarithmic. In this case, the change to "10%" will be perceived quite differently from the initial entry level. For example, from 20% to 30%, the subjective level change will be large. From 70% to 80%, subjective level changes will not be large.
Analog controllers often use a linear volume change, similar to digital (software) volume controls in percent. In practice, the maximum value of 100% can be established where only 90% is visually visible, and instead of 0% there will be no complete silence, and approximately 1%. For analogue controllers, the calculation will be approximate, not exact.
In a more serious technique, the loudness values are expressed in decibels, where the maximum is often taken as 0 dB and all the values for the volume down are negative. In rare cases, for 0 dB, not a maximum level is designated, but a standard one with the possibility of additional amplification upwards.