Well E1H is the block right next to their support and divided by a gangway. I suspect they were always going to use half of that block for segregation (as you can see they have done by looking at the ticket selector) but sell the other half of the block to one club or the other, depending on...
Well until @erkan's post above, I'd have assumed they'd keep a ESL block back that was adjacent to the away end and only sell those last minute. If he's right, Grimsby won't be getting more tickets.
That is my gut feeling too. In which case, if it looks like that is happening then I hope the club releases a few more to Grimsby in the final few days. Wouldn't begrudge them another 500 tickets if we can't sell them.
I'm curious to know whether they are going to leave a block or two spare near the Grimsby fans. i.e. if we don't sell out, would they give Grimsby a few more tickets.
I expect it will sell out to home fans, mind. But you never know.