If you read the article
https://www.etsy.com/help/article/198?ref=help_search_resultit will tell you all about renewing.
Basically when you renew an item its listing date becomes the date that it was renewed and it will then expire four months from that date.
You are expected to have read and understood the Terms of Use
https://www.etsy.com/help/article/479when you created your account.
When you renew a listing it does state that
When you renew a listing a yellow box pops up that says
""This will cost a non-refundable fee of $0.20 USD. By clicking “Renew” you agree to pay this fee.
The listed on date will reset to today, and the expiration date will be four months from today.""
which should be sufficient notice.