Workflow start only when item is modified

Hi guys, 

I'm a new member/user of the Nintex application and this community so I would be very thankful if you help me out here, or at least provide me a link where there is an answer of my question below.
I have 2 different workflows created for the same list. One of them I want to be started when the item is created and the other one only when the item is modified. But, the second one ( start when item is modified ) I want to be started only when the first time the item was modified, which means once.
So, even though I have sucedeed with providing this functionality with additional temp column was involved, I have noticed very strange thing here which honestly I didnt expect: 
Every time after the ''Start when item is created" workflow was finsihing the second workflow 'Start when items are modified" was starting automatically even though the item have still not been modified.
Any idea why is this happening, why the order of the events receivers are replying to the Nintex workflow?
I expect when I choose the worklow to be started only when the item is modified to be started only that time and not in this way.

Is this is how the Nintex workflows are running and we need to adapt to that thing?

Thanks in advance,
Jovica