Barry
It works like co-ordinates. To start, you are in Parcelle B which is obvious right?
Then, the larger numbers work the x-axis (left to right) and the smaller number the y-axis (top to bottom). Ignore the numbers in the pitches themselves and refer to the black scale. In this case your pitches look like they face each other across an access path and have the numbers 89 and 91 in them respectively (the 5th pitches up from the main red shaded blocks).
Smokie - you will be higher up (if you extend the y-axis in descending numbers) and further to the right in the same parcelle. In this grid shown you are on the right hand most strip (the number in your pitch is actually 98). Your sold pitches will be in a 2x3 rectangle above you.
For clarity, B1 would be the strip of pitches that run along the top of the picture.