How to add a dimension "SUMMARY", used in Jira Service Desk tickets

I can not add as dimension - it does not let me tick this box.

Also from the Knowledge base document is is written sumry instead of summary, is this correct:
[jira.customfield_sumry]
name = “Summary”
data_type = “text”
javascript_code = ‘’’
if (issue.fields.summary) {
issue.fields.customfield_sumry = issue.fields.summary;
}
‘’’