It’s not part of GDL itself. Archicad will substitute all references to autotext fields in whatever GDL output it finds them.
For example, if you write <PROJECTSTATUS> in the parameter string of a text2 command, will nicely replace it with the actual value.
All this is invisible to GDL – consequently the size and other attributes of the text are not measurable.
PROJECTNAME
PROJECTNUMBER
PROJECTSTATUS
DATEOFISSUE
SITEFULLADDRESS
SITEADDRESS1
SITEADDRESS2
SITEADDRESS3
SITECITY
SITESTATE
SITEPOSTCODE
SITECOUNTRY
KEYWORDS
NOTES
ARCHITECTNAME
ARCHITECTPOSITION
CADTECHNICIAN
ARCHITECTCOMPANY
ARCHITECTFULLADDRESS
ARCHITECTADDRESS1
ARCHITECTADDRESS2
ARCHITECTADDRESS3
ARCHITECTCITY
ARCHITECTSTATE
ARCHITECTPOSTCODE
ARCHITECTCOUNTRY
ARCHITECTEMAIL
ARCHITECTPHONE
ARCHITECTFAX
ARCHITECTWEB
CLIENTNAME
CLIENTCOMPANY
CLIENTFULLADDRESS
CLIENTADDRESS1
CLIENTADDRESS2
CLIENTADDRESS3
CLIENTCITY
CLIENTSTATE
CLIENTPOSTCODE
CLIENTCOUNTRY
CLIENTEMAIL
CLIENTPHONE
CLIENTFAX