Write a question about the following article: The organisers estimated that about 15,000 volunteers are needed to successfully host the games. Volunteer recruitment began in late 2013, and by February 2014, about 5,000 volunteers have signed up. This number swelled to over 17,000 by February 2015, and a volunteers night event was held at Universal Studios Singapore to launch the sports volunteers brand name as "Team Nila" and to thank the volunteers who have signed up with free shows at the venue. Amongst the pool of 17,000 volunteers, 35% came from the community, while 65% were from corporations in support of the games.

Question about the article:
How many more volunteers signed up between February 2014 and February 2015?