A tag, just like a ticket can have four "coupons". But, nothing limits "conjunction" tickets or tags other than the carrier's willingness to issue them.

It is not out of the routine to see 6. You will simply see a second tag stapled and, if you had a bar code reader, the first tag would have an indicator that the fourth "coupon" is not the final destination.

All of this dates to the time when tickets and tags were carbon forms and there were only so many impressions that could be made and still read.

I know that people worry about multiple connections, but there is no reason that any one bag transfer is more risky than the next transfer (other than the particular station itself).