Thanks for your posting.
- Forecasting takes into account both the Estimates and Elapsed values but the forecasts get more accurate the more Elapsed values you enter on the Add Test Result dialog. Filling in just the estimates would be sufficient to get the forecast and progress features to work though.
Also, you wouldn’t need to enter estimates for all your test cases and it is enough to add estimates for 20% or so of a test suite. Provided that the test cases take a similar time to execute, TestRail can work with average estimates and this should result in good forecasts as well. But again, the more numbers you enter the better the actual forecasts will be.
- Yes, TestRail takes into account the amount of tests you can process and how much time you can spent on the tests per day. This is called the velocity and is one the key attributes to calculate a good forecast for a test run/plan or milestone. So, the faster you are progressing on a test run/plan or milestone, the earlier the forecast will be.
I hope this helps and please let me know in case you have any further questions.