Another example of the implication of the system.
First of, each division in the screenshots use 1,02 supply. This is deliberate, so it's easy to follow how much supply is being requested by the army at a glance.
I built a supply hub on the border between Siam and Singapore, i consider this to be very reasonable considering the Japanese can Ally Siam through a focus prior to attacking the Allied powers.
Screenshots in order, with some explanation
Screen 1: The Japanese has set up a supply depot, and a sizeable army on the northern border to Singapore. Deploying 25 divisions, consuming about 25,5 supply. The entire army is 100% supplied.
The British army has set up 30 divisions, using about 30,5 supply. All the divisions are fully supplied. The units have been set up to offer resistance at the border, especially at the north-western port. The army continues south, along the important railway connection and the adjacent tiles. The Eastern port has been fortified, as has Singapore itself along with the air field immediately north of Singapore city. 4 unimportant tiles have been left undefended.
Screen 2: The Japanese has pushed the border, and captured the port. A railroad has begun construction, to integrate it with the Siamese railroad network. The Japanese army is fully supplied.
The British army has fallen back, forming a new defensive further back. Most of the army is behind the river. Supply is still 100%.
Screen 3: The port of Kuala Lumpur has fallen. The British has been pushed back, and the loss of this vital supply hub has seriously impacted the Brittish ability to maintain formation so far away from the now only remaining supply hub in Singapore itself. The two front line tiles, can only supply three divisions each.
Screen 4: The British army has pulled back, in order to more efficiently supply it's army... would be the realistic outcome. However, in game. Moving your army closer to the supply hub, has in fact the OPPOSITE effect. The British army has starved itself of supply by moving closer to the source of supply.
At this point on, each additional JUNGLE tile lost. Reduces the total available supply in the area, the hub has a maximum throughput of 31, that is how much supply it can receive. But it only receives 24, because the units ARE NOT FAR ENOUGH AWAY FROM THE SUPPLY HUB!
Edit:
Proposal for fix.
Supply hub should ALWAYS have maximum supply available. There should be no possible scenarios, where Singapore has less than the maximum of 31 as shown in the screenshot. Then tiles further away from the supply hub, should have a % of the maximum available on the hub as potential supply.
Supply ''region'' has 30 supply. This is constant, it cannot be reduced as long as the logistics line is undisturbed.
Hub = 30 supply, cannot be reduced.
+1 province = 24, 80%
+2 province = 18, 60%
+3 province = 12, 40%
+4 province = 6, 20%
Just some example numbers. Adjust based on terrain, trucks, weather, and other factors.