Apparently "Tipo" is the Identification Document Type:
- C.C: Cedula de Ciudadania
- C.E: Cédula de Extranjería
- N.I.T: Numero de Identificacion Tributaria
The "Cedula de Extranjeria is is apparently given to visitors who are staying over 3 months, so as a regular tourist, I can't enter any meaningful data in that field.
After entering "1234...", I was forced to register a Colombian phone number (which I don't have, given the ridiculous registration required to get one, when I already use Google Fi), so Mercadolibre lost another customer.
(the '+57' is not changeable)
UPDATE: I used a friend's Colombia number. Now Mercadolibre wants a PHOTO OF MY CEDULA. They can sod off :)