It should be more than enough for a web site that is not excessive in size (amount of pages) or daily traffic. For your site to use more then 250 GB per month of data transfer your site would have to be receiving a very large amount of visitors on a daily basis and/or have many pages that are being accessed.
Example: Every time one of your web pages is viewed by someone on the internet, the size of that page goes towards your bandwidth usage.
Below is an example of how many times a page would have to be viewed in a month to reach 1 GB of bandwidth...
page size 20 kb = 50,000 views
page size 30 kb = 33,333 views
page size 40 kb = 25,000 views
page size 50 kb = 20,000 views
Calculate Bandwidth Usage: