If your connection was interrupted during the download process, you do not have to worry about being charged again. Just go through the download process again, and the Shop will prompt you to "confirm your in-app purchase. Click "Buy" to confirm and another pop up will say "You've already purchased this, Tap OK to download again for free" and you should be all set.
Due to the number of users downloading at the same time as well as the large file size of the preset pack, we suggest you process your download(s) with a strong internet or cellular connection and that your auto lock setting is turned "off" - if your device automatically has an auto lock setting that puts your device to "sleep" it will interrupt your download.
That being said, if you happen to receive any notifications during your download process such as a phone call, text message, FB, Instagram, Twitter, etc. do not open the notification as leaving the download page will cause a connection error and could result in missing or corrupted preset.