Weapon upgrade transfers

When I transfer my upgraded weapons ,why doesn't the increase with the weapon I have upgraded increase its upgrade as well for example 1st weapon is tier 4 upgraded +20 2nd weapon is tier3 upgraded +45 transfer over to 1st weapon & becomes tier 4upgraded +45 shouldn't the weapon become tier 4 upgraded +65,what's up with that? They can't do math or what?

Oiii..

Oiii..

If you can do it, you can break through the limit without using stones. Move to other weapons of +0 and strengthen one weapon with various stones.

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