That's very odd.
I tried it 3 times, and every time I tried it worked out exactly as you thought it should. Here's one of my tests:
Turn 1:
1760/2000
1800/2000
1840/2000
1840/2000
1840/2000
2800/3000
2800/3000
2920/3000
2920/3000
7800/8000
Total 28320/30000
Turn 2:
2000/2000
2000/2000
2000/2000
2000/2000
2000/2000
3000/3000
3000/3000
3000/3000
3000/3000
6320/8000
total 28320/30000
I did it multiple times, with different numbers, and every time it only took supplies off the big supply ship until it's supplies were on par with the rest of the ships
I wish I could offer an explanation as to whey yours turned out as it did... but... I'm at a loss.
