How To Calculate The Plan For Iphone

I'm planning to get an iphone with a classic plan and broadband on mobile value. Singtel says that it can be used to retrieve over 200 emails per month, surf over 300 WAP pages and download 5 songs. What does it mean? Is it i can receive approx 200 emails, open 300 pages and download 5 songs from itunes? Do you think it is enough? I don't use a lot, just average.