This question also worries me and it is hard for me to understand, what is the reason for it? Anyway, it all seems very interesting for me, that's why I will try to find out more about it. If you want to have a private talk with me, you can always send me a message or find me in the college essay division, where I am working as a writer findwritingservice.com/college-essay.

It should not be a worry, and its not hard to understand once you learn and remember the reasons why.

First there is a trade off  between what the troop can carry,that is troop capacity, and how fast it moves.

Anything that involves horses are fastest and carry the least.

Anything that involves wheels are the slowest and carry the  most.

Also you start off the game with the quickest set of troops T 1, and as you can train different levels of troops they can carry more but move more slowly than the previous one.

Your troops and your hero start off with the lowest amount of skills ,which by training and learning knowledge these skills increase.

Additionally troops sent with the hero can always carry more than those sent without.

Also when sending out the hero with the troops , what the hero is wearing can also affect total yield and time of yield.

Lastly. 

There are some days , when the game will increae Troop capacity.