If you have set the number of Tweets to display in the Widget options for Simple Twitter Tweets and yet you are still seeing the original number of Tweets displayed when you loaded the widget, it may be because your hosting provider is over subscribed (they have accessed too many Twitter Tweet streams within the 5 minute allocation).
This happens a lot on shared hosting and busy gateways. If this is the case, the Tweets being displayed on your site are being presented from the database store of your last successful call to the Twitter Application server.
Please give it time and see if this changes once access to the Twitter service is again restored.