Actual Size on Monitor is Not Accurate

I believe Marc Autret may have a script that assists: https://indiscripts.com/category/projects/PhysicalSize

Wait again... both scripts are correct but my description is bollixed. (Curses not being a Script Wizard™!)

The short script will instantly set your display to true 100% display, one inch to one inch, but by changing the zoom percentage. Set the '115' value to whatever gives you that exact screen measurement.

/* SetRealScrnPercentage100 */
try {app.layoutWindows[0].zoomPercentage = 115 } catch (e) {};

(I can't remember if this is another script of Rob's, or from Bob Levine.)

The one you want, to adjust your screen rez to an odd value and get that 1:1 correspondence for your 100% zoom setting, is this one. Just run it and enter adjusted values until you have 100% display at the 100% zoom setting. It's a sticky setting and will persist at least until major updates; if not, re-run it with your established value as needed:

/*
* Set a custom display resolution
* Rob Day 2020-2022
*/
var mm = app.generalPreferences.mainMonitorPpi.toFixed (2);
$.writeln(Number(mm))

makeDialog()
var cRes, ckBox;
function makeDialog(){
    var theDialog = app.dialogs.add({name:"Display Resolution", canCancel:true});
    with(theDialog.dialogColumns.add()){
        staticTexts.add({staticLabel:"Custom Resolution:"});
        staticTexts.add({staticLabel:"Use System Setting: " + mm + "  "});
    }
    with(theDialog.dialogColumns.add()){
        cRes = realEditboxes.add({editValue:Number(mm), minWidth:100});
        ckBox = checkboxControls.add({checkedState:false, minWidth:150});
    }
    if(theDialog.show() == true){
        cRes = cRes.editValue;
        ckBox = ckBox.checkedState;
        setCustomRes()
        theDialog.destroy();
	}
}


/**
* Discription 
* @ return value 
* 
*/
function setCustomRes(){
    if (ckBox) {
        app.generalPreferences.customMonitorPpi = 72;
        app.generalPreferences.useCustomMonitorResolution = false;
    } else {
        app.generalPreferences.customMonitorPpi = cRes
        app.generalPreferences.useCustomMonitorResolution = true;
    }
    app.activeWindow.zoomPercentage = 100;
}