Back from the dead
Here's a little humor... This page has Capt H. Dunkerley killed in action on 23 March and buried 2 days later. This page AWD0003y2p has Capt H. Dunkerley alive and kicking on 13 April, promoted to Major and commanding a section of an ambulance.
I checked CWGC, and it shows him killed on 23 March--- https://www.cwgc.org/find-war-dead/casualty/585527/dunkerley,-/
I've been doing this diary for 200 pages and there has been only one Capt H. Dunkerley, but just in case I checked LFWW to see if there was another Capt H. Dunkerley at the time. It doesn't have any Capt H. Dunkerley, but has him as Major H. Dunkerley, killed on 23 March--- https://livesofthefirstworldwar.org/lifestory/2396730
It's strange the both LFWW and CWGC have him as Major, when he's been Capt all the way through this diary, except for that quizzical entry on 13 April.
The adjutant must have made a mistake, intending to write some other Captain's name, but for some reason was still thinking about Dunkerley, who had died 3 weeks before.
Here is an article re Captain Harold Dunkerley RAMC
Diary page states buried at Blaireville 51c X.4.d.4.9.
From the Hospital Gazette Obituary page 109 with photo.
Link: http://www.meaningsofservice1914.qmul.ac.uk/sites/www.meaningsofservice1914.qmul.ac.uk/files/sites/default/files/record_files/London Hospital Gazette_22 1918 Issue 198 Part 2.pdf
For a Major Harold Dunkerley this link states Cemetery/Memorial: CABARET-ROUGE BRITISH CEMETERY, SOUCHEZ, Pas de Calais, France https://livesofthefirstworldwar.org/lifestory/2396730
by cyngast moderator
I think what might have happened is that the process for making Capt. Dunkerley an "acting major whilst commanding a section" was underway when he was killed. The second page you posted says this went into effect on 1 April, which is only about a week after 23 March. Maybe it's possible that wherever the decision was made to make him an acting major didn't receive notice of his death. The field ambulance probably didn't get the official notice of this until 13 April, when it was duly recorded in the diary.
So could he have been officially promoted to Major posthumously?
BTW, I don't have any references for my hypothesis here. I'm just thinking about how large organizations work and how things still cross each other in the mail today. Throw in some confusion caused by being on the Western front at a place and time when the Germans were mounting their 1918 Spring Offensive and it's possible to see how this kind of information could get tangled up.