The formula for activity point (it is the 2 week period was mentioned by @jackg)
The activity number is determined in this way:
time = number of two-week periods in which you've posted since your registration
activity = min(time * 14, posts)
Many old era Junior members were demoted to Newbies in June 2018, you have 2 merits and you have passed through the hardest challenge for newbies. Now, you can keep up your learning forum, bitcoin and try to help others if you can. Don't spam as it is the barrier from your side in ranking up progress.
You will be a Jr. member next 2 or 3 weeks. You created your account in March 2020 but did not make any post till the last week (3 Feb 2021).
The restriction on images were applied in 2017.