Could you try to expand the description and check if the EUR still can edit the value?

Because to me, it's working fine try to increase the size of electrum wallet and maybe the description is behind the EUR amount that is why you think that you are editing the EUR value and let me know if what version of the wallet are you using?

Mine, I'm using electrum 3.0.6 and it works fine, but if expanding electrum doesn't work just report the issue here https://github.com/spesmilo/electrum/issues

So that they can take action and release a new version.