(Reuters) - Grocery delivery app Instacart raised its proposed price range for its initial public offering (IPO) on Friday, revising its terms to target a fully-diluted valuation of up to $10 billion following a stellar debut for Arm Holdings.

The price hike signals robust investor demand for the San Francisco-based company, which is looking to list its shares this month after years of waiting in the wings.

September is gearing up to be one of the busiest spells for new listings.

Shares of SoftBank's chip designer Arm were up nearly 3% in volatile early trade on Friday, extending gains from their strong close on the first day of trading.

Another portfolio company of the Japanese investment giant, Neumora Therapeutics, is set to start trading, while marketing firm Klaviyo is looking to list in the next few weeks.

Traditional U.S. IPOs have raked in more than $5 billion so far in September, according to data from Dealogic, already the second biggest month for such share offerings this year.

Instacart said 22 million shares will be sold at $28 to $30 each compared to its previous price range of $26 to $28 each. At the top end, the IPO will fetch $660 million compared with the earlier target of $616 million.

Of the total proceeds, up to $237 million could go to existing Instacart investors looking to sell their shares.

The company's raised valuation target, however, would still be just one-fourth of the $39 billion it was worth after its last funding round more than two years ago.

Cornerstone investors have indicated they will buy up to $400 million worth of shares, which would account for around two-thirds of the total proceeds if they were priced at the top end of the range.

(Reporting by Niket Nishant in Bengaluru; Editing by Krishna Chandra Eluri and Arun Koyyur)