Fill into a character field a single value from an array


I have an array in the vendor table that contains multiple values. 

what i need is to select a value from this array into the incident record after i select the vendor.

I added a link line but my issue is the field i want to fill into is character. 

so the fill brings {1,2,3} the whole array into a single field , how can i select only one value from it .