This only affects overlap checks but not casts. When using physics 2D overlaps with an attached tag text the default behaviour is that the text size is relative to the shape size.
This leads to text getting smaller when the shape is farer away from the camera.
It may be desired that the text is readable independent from how far the shape is away from the camera.
This can be achieved with this global setting that forces all text at drawn overlap shapes to a fixed screenspace size.
The default value of 0 means "constant screenspace text size is disabled".
The value defines the width of one text letter relative to the screen height, so e.g. a value of "0.05" is suitable in many cases.
This uses DrawBasics.cameraForAutomaticOrientation to choose the camera screen to which the text size gets fitted.
This setting competes with the forcedConstantWorldspaceTextSize_forOverlapResultTexts setting. If both settings are activated (that means set to something else than 0) then "forcedConstantScreenspaceTextSize_relToScreenHeight_forOverlapResultTexts" wins and "forcedConstantWorldspaceTextSize_forOverlapResultTexts" is ignored.