'Page' represents the 's.pagename' variable of Reports & Analytics and hence would return whatever value you have collected in this dimension. If you don't pass any value in this variable in your implementation, then it by default captures the URL. This variable has a limit of 100 bytes hence characters post that are stripped.
If you are looking to get URL values via API, I'd recommend using the 'pageURL' element. However, please note that it's only available in Data Warehouse API hence please ensure you specific 'warehouse' as the 'source' within the payload.
Thanks for the reply. You was saying that maximum length of the url return by requesting page element is 100 bytes. However i was able to get URL length up to 225 chars based on my testing. I also called the support yesterday, she told me that URL return by requesting page element and pageURL from datawarehouse are the same. I would expect to get more exact answer in this case.