Hello @dvanderper,
Do you mind asking your questions in English please, so other users can understand this as well? 
So you’re asking how to change the value of for example the final stock?
The code that generated the value of final stock, is this :
{% t "Eindvoorraad" %} {% input custom.detail.eindvoorraad as:account_collection range:6,7 accounts_var:eindvoorraad %}
It’s in the accounts_var ’ eindvoorraad ` all accounts will be put in, to generate the value of final stock.
If you want to make this overwritable, first you’ll need to create a new input-object, fi :
{% input custom.ev.waarde as:currency %}
This however will only create an input-object where a value can be put in, but of course you want a value already being put in there automatically, but that’s still can be overwritten, right?
So, the value you want in there automatically, is the value of the accounts_var eindvoorraad. you can summon that by adding .value to the accounts_var :
eindvoorraad.value
This will give the total amount of every account selected in the accounts_var by the hashtag # .
So by using a placeholder_default to your input-code you’ll be able to display the total value of the accounts_var but it’s still overwritable :
{% input custom.ev.waarde as:currency placeholder_default:eindvoorraad.value %}
Can you give it a try? If you’re totaly new to Silverfin Templating Language, it’s advised to go through this here first.