How to display only the value in edit page in Active Admin

As Alex said, set to disabled. You could then use css to get the visual you wanted, if you can live with the semantics of that.

The syntax was slightly different for me to get this to work.

in your admin form:

 f.input :finish_position, input_html: { disabled: true } 

in your CSS active_admin.css

input[disabled="disabled"],
input[disabled] {
  background-color: #F4F4F4;
  border: 0px solid #F4F4F4 !important;  
}