The statistics of the penis DB say that only 5 guys have ever claimed to gain 3.5 inches. If you assume that your initial measurements were correct, that would put you in the top 99.7% of those gainers. From a percentage growth perspective, nobody in the database claims to have doubled their length. The most is 78% and 40% would still put you in the top 98%. If you assume that your measurements were off and maybe you really started at 4.5”, the numbers don’t change that much.
However, I do think it is highly likely that your first measurement was not maximal, but you also probably grew some in the first week and a half. I’d guess you were really closer to 4.5” or more. It is totally reasonable to say that you could grow as much as the top 75% percent of the people in the db. That is 17% relative, or 1 inch absolute measurement.
On average, girth is gained at about half the rate of length.
Some guys grow like crazy, though. You could be one of them. I filtered the data to look at guys with less than 4.75” starting measurement and the following names stick out as exceptionally inspirational:
Invisible 4.640 -> 5.820 + 1.180
WarmGun 4.720 -> 7.090 + 2.370
Langemann 3.940 -> 6.300 + 2.360