RMAs link also says that it was a stand-alone AND a freebie in the magazines, but the freebies were usually only seven pages long. The auctions I posted show scans of page 12 & 15 respectively. The link to the auction at the top of the page mentions that each of the magazines contain 7 page Sonic stories. Starting to tie together.
Looks like the stand alone has 15 pages & the magazines have seven pages printed in the magazines themselves. At first, I thought the magazines contained a removeable comic that was the same size as the mini, but I no longer think that is the case. Plus, if these were 'inserted' into the magazines, I would think that any copies removed would look like hell.