The tone curve in Lightroom operates via mouse movements. You cannot input numbers to the tone curve.
When you have the "Point" curve optioned- (click on the point curve icon- bottom right)
You can click on the curve to "Set" a point.
When you hold the cursor clicked on a set point you will see the from/to percentage coordinates at the top of the tone curve box.
For example to set 81/80 click a Set point and move it on the curve until you see 81.0/80.0 % at the top- as in this screen clip- (it shows 82.4 / 80.0 % )
I have set the four RGB points similar to your values in your screen-clip.-
(Error in this screen-clip above!!! the Channel selection does not appear if your are developing a PSD file!)
For a RAW, TIF or JPG the Channel selection is visible-
To set the individual Color channel curves-
First open the drop-down menu beside [Channel :] to select the color channel, then repeat the procedure to set points to the wanted values. Repeat for each color channel- Red Blue Green.
eg. this is BLUE point 69/67 (The curve shows 69.4 / 66.7 % )
When you have set all the values in the example in your post- the first step should be to save a Tone Curve Preset and your settings will be easily re-producible.
Previous post deleted-I thought you were trying to enter 0-255 RGB values. Sorry for any confusion!
In addition to wobertc's suggestions holding the SHIFT key locks the curve point X axis value, which makes it easier to set the Y axis value.
holding the SHIFT key locks the curve point X axis value
I learn something new every day.
And holding [ALT]- makes the mouse movement much finer for more accurate positioning of the set point.
hey gusys thank you all so much