Ollie I have taken a crop of your base image and had a play, and attach 2 how I got there graphics and the end result.
Looking at the histogram shows that there is quite a bit of space towards the left side that has no info. Clicking the Double Threshold box shows a few black pixels but no white ones.
As the image contains white it is necessary to move the white point slider to the right until some white pixels appear. You have two options here. You can drag the left hand handle on the bottom histogram to the right until pixels appear or select the levels and curves and use that histogram. From the graphic you can see that the ' Levels & Curves ' one is larger and may be more convenient to use. Either way same result.
Ensure you have the Double Threshold box checked and only move the slider until the first few white pixels appear. At this point you can uncheck the box and see how the image appears. If OK then fine. If not quite then either tweek the slider or OK that operation and then select White point, and you can use the adjustment slider on that to fine tune the result.
Step 2 was to set the Black point. Again it is important to use the Double Threshold and magnify the image to ensure the point you set is on a collection of black pixels. If it is half on and half off you will have to use the adjustment slider to get the desired result as the result will be too dark.
As the image had a warm tone I magnified it and found a nice grey pixel in the corner of the number 5. I paced a Neutral point here to remove the cast.
It may not be quite the result you want, but it hopefully gives an idea of how go about achieving it.
No doubt my mentor Foxy will say if my method is not correct.
Don