Customs rules in India state (the 'free allowance' referred to is for personal items, and the duty-free allowance of alcohol cigarettes):
One laptop computer (notebook computer) over and above the said free
allowances mentioned above is also allowed duty free if imported by
any passenger of the age of 18 years and above.
- You can bring your new Lenovo laptop duty-free under this allowance.
- Since your Macbook was bought within India, you don't need to pay
customs duty on it. However, you may be required to provide proof that you bought it in India.
EDIT: It seems that an invoice isn't valid as a proof of purchase. Specifically, you'd need to get an 'export certificate' before flying out of India.
If a passenger going abroad is taking any item (non-commercial,
personal, private property) as baggage which is intended to be
re-imported into India on a later date, to avoid paying Customs duty
on that item during such re-importation, the passenger should ask the
Customs at the departure terminal to issue an "Export Certificate" in
respect of that particular item.
Any dutiable item, even if taken out from India, shall attract duty unless accompanied by a valid "Export Certificate" issued in the name of the passenger or in the name of any member of his/her family.