From the help files....
System-generated, protected field. Displays one of three prime line types: single line, key system or multicall (note that the information entered in this field matches the corresponding entry in the Multiline IP Sets form or the Multiline DNI Sets form).
"single line": The set's prime line is a single line – it is dedicated to one telephone only.
"key system": The set's prime line is a member of a key system group. A key system group is a group of Mitel multiline telephones. One industry standard telephone may be added to form a mixed multiline group which shares a specific line appearance. When a call is directed to the number associated with the Key System Group, all sets in the group will receive the indication. Once a set answers the call, all other sets in the group will see the corresponding line as busy. A fictitious Directory Number may be used to create a key system group. This means you may set up a directory number which is associated with a key system group rather than a system device. Associate a previously unassigned directory number to the line select keys through the key assignment form.
"multicall": The set's prime line is a member of a multicall group. A Multicall group is a group of Mitel IP telephones. One industry standard telephone may be added to form a mixed multiline group which shares a specific line appearance. When a call is directed to the number associated with the Multicall group, all idle sets in the group will receive the indication. Once a set answers the call, all other idle sets in the group will still have access to the line either to answer or originate calls. As with key system numbers, a fictitious number
Which is where my confusion arises from....since the key was programmed as a single line?