How does Upgrades really work?

[Alry FireBlade]

I am planing on making the Heros in my Map stronger with the use of "Custom" Upgrades.
The basic on how to use it are already known by me, my only Problem is I can't find out what some stuff means.

The Upgrade for Attack Damage Bonus has 2 Datas I can edit.
1. Attack Damage Bonus - Increment
2. Attack Bonus - Base

The second one is clear to me, I guess. This is the basic value it adds. For example, when a Unit has 10 AD (Attack Damage) it goes to 20 AD.
I thought when I put a let's say 10 to the Increment, every Upgrade gives 10 AD more, but no. For level 2 this stays true, but then the amount of AD does not increase any more...
What really confuses me is, that when it comes to the gold and lumber cost, they work like I would expect.

Can someone maybe explain that to me?

Here are the stats I am talking about:

 

[Nichilus]

'Attack Base Bonus - Base' = the damage increase for first level
'Attack Base Bonus - Increment' = the damage increase for any other level after the first one.

I am on latest version and I have no such problems that you describe.
In fresh map I have created a copy of the 'Iron Forged Swords' upgrade, changed the effect from 'Attack Dice Bonus' to 'Attack Damage Bonus', gave it 10 levels and set this upgrade to be used by a hero and non-hero unit.
Then I used this trigger in game to test it:

• Untitled Trigger 001
  • Events
    • Player - Player 1 (Red) skips a cinematic sequence
  • Conditions
  • Actions
    • Player - Set the current research level of abc to ((Current research level of abc for (Triggering player)) + 1) for (Triggering player)

Result: damage of both hero and non-hero was increasing as expected