That's spot on - its exactly what I wanted.If you’re not concerned about 55% efficiency we can move on. If you want to improve your efficiency there are things you can do. Some immediate observations:
Your mash is quite thick, you could use more water in the mash and less for the sparge.
The volume of mash + sparge water is 34 litres but you only get 23 litres into your kettle. You can work on absorption by the grain being 1 litre of water per Kg of grain (it’s actually a little less in my experience), this might account for 5 litres but there’s still a big gap. Are you leaving this behind in your mash tun? Most people find a way to tip the mash tun and/or gently press the grain bed to extract more wort.
You lose another 6 litres in the boil kettle so you could try a less vigorous boil (a rolling boil is good enough), a shorter boil (45-60 mins?), and maybe leaving less wort behind in the boil kettle. Leave the cooled wort to settle for a while maybe so the sludge is more compacted in the bottom.
There are other considerations but these might be a good start.
Obviously the 55% efficiency is quite striking and not what I wanted (!).
My recent upgrade has been converting a drinks cooler to a mash tun which has helped massively with temp. control, but as it was my first time using it yesterday. I probably did too thick of a mash and didn't extract all the water post-sparging. I am aiming to get another brew on once this ones out the fermenter so will bear in mind all your pointers for better efficiency and give an update. The rolling boil is a great shout, and I usually try shift the wort straight to the fermenter once its cooled so I will try leave it longer to settle out the sludge.
In the meantime, how have your brews been going?