The phrase "extra porter" typically refers to an additional person hired to carry heavy items, such as bags or packages, alongside a main porter. Full definition
An extra porter to carry your personal items: US$ 75.00 / 4 days; (incatrail-peru.com)
- Unless you hire an extra porter you need to carry your back pack, sleeping bag and the mattress. (sastravelperu.com)
if you want an extra porter (for the full trip) you must have booked this with your original booking form as they require permits as well. (sastravelperu.com)