There is a default max of 1000:
The maximum number of objects to be returned per call (page size). The default is 1000.
Take a look at the documentation here:
Roger is right. I thought I would add the following syntax to help anyone following this thread:
If you code in '5' for your maximum number of points you will get 5 points back. If you code 5000 you will of course get 5000 points back.
thank you both for your help! I noticed that there is also a startIndex parameter, which used in conjunction with the maxCount parameter allows the definition and navigation of pages for the feed of data points. It's a shame that the Web API does not explicitly show that more data is available by providing a link to the next page.
Thank you for the telling us (me) about the startindex parameter. I can see that being useful. I tried it and it worked great.