how exactly works axis label position and extent?

I want to place horizontal y axis labels so they do not overlap with axes and keep nicely preserved for print. Small example:

figure();
subplot(2,1,1);
plot(rand(10,1));
h = zeros(2,1);
h(1) = ylabel({'Short';'label'});
subplot(2,1,2);
plot(rand(10,1));
h(2) = ylabel({'This is a long';'label of y axis'; 'three-lined'});
set(h,'Rotation',0);

To resolve the problem, I reposition axes to the right to make space:

hxs = get(gcf,'children');
apo = get(hxs,'position');
apo = cell2mat(apo);
marga = 1 - (apo(1,1) + apo(1,3));
npo = apo;
npo(:,1) = apo(:,1) + 0.8*marga;
for ii = 1:length(hxs)
    set(hxs(ii),'position',npo(ii,:));
end
clear ii;

I reposition the labels. Based on what I could find in documentation and internet, I only know to do it ad hoc way:

lpo = get(h,'position');
lpo = cell2mat(lpo);
adj =  0.8; 
nlp = lpo;
nlp(:,1) = lpo(:,1) - adj; 
for ii = 1:length(h)
    set(h(ii),'position',nlp(ii,:));
end

Looking on the labels extent and position, I come up with a guess for "adj" of 0.8.

Instead of guessing, I want to derive a good "adj" based on the dimensions of the labels and/or objects these relate to.

Please can someone explain what is axis label position and extent? What are the units? What do they relate to, axes, and how?

Thank you.