ServiceNow, How to populate value to a list variable

I am using ServiceNow develop instance to create a table, in which one field is type of list. The values of the list is populated by Outgoing Rest message.

In business rule, I make a hard coded to see how list values shall be what kind of form. The codes lists as below/1/: but when I update the field computer room, the computerlist’s value is not populated. It looks like in the image/2/. How to populate values to a list type of field?

/3/ is the json string returned in pretty format. I try to populate hostName to computerlist, but failed.