You'll have to format your external SD card as ExFAT - the FAT filesystem has a maximum file size of 4GB. (It's due to the size of the number used for file size - it only has enough bits [digits] to hold a number 4GB - 1, like 3 decimal digits can only hold a number 1,000 - 1.) You may also have to use a different method of file transfer - if Android File Transfer for Mac uses the same length number, it just won't transfer files larger than 4GB. Dragging the file from the Mac (do they still call the thing you see files in "Finder"?) to the phone's external card - if you plug the USB connector directly into the Mac, not into a USB hub (most of them overheat on sustained file transfer and quit) - would probably work. (As long as the card is ExFAT.)