You can't retroactively change data.. but also Web Analytics doesn't work like that... you can't track subscribers like a ever climbing counter.... subscriptions are constantly up (as new people subscribe) and down (as people unsubscribe)...
You also need to consider that in 2 years (or whenever your data retention policy is set to truncate data), if you were trying to do a "constant counter" would start to fail once the older data is truncated.
You need to think about Subscriber Data as "what is the state now"...
Meaning:
1. Track Successful Subscription Events (and Successful Cancellations) - look at these values daily, weekly, monthly, yearly... but get a sense of additions and removals....
2. When users are logged into your site, track if they are subscribers or not... then you can create reports daily, weekly, monthly, yearly etc, of "Active Subscribers" within the time frame.
Web Analytics is about the period you are checking... not about trying to keep an all time running tally of who is what (that is what your actual user Data Base is for... people can query right now, who is subscribed, who is not subscribed... those are your counts)... Analytics is for seeing who is active, at what time frames, are trends of adds going up or down, are trends of cancellations going up or down, what is the percent of subscriber vs non-subscribers for active users in a set time, etc....
