There are four named contracts in the charge. Marvin Johnson and John Lundstram, both from 2017 and Callum O'Dowda and Kemar Roofe, both from 2016.
It is interesting that the O'Dowda and Roofe contracts are there, as often transfer fees are paid in two instalments, the initial payment and then the balance 12 months later. This would mean that the O'Dowda and Roofe monies had already been received by the time of the charge, so it is reasonable to assume that the reason they are mentioned is that there are sell-on/performance payments in their contracts. To my knowledge there is a sell-on clause in O'Dowda's and a promotion bonus in Roofe's. It could, of course, be that the O'Dowda and Roofe fees are due in more than two instalments?
What all of this means, in simple terms, is that a set amount of £4.2m is owed to Ensco and the club have certain stage payments to make (which interestingly add up to exactly £1m less than the sum due). The club can choose to pay these from their normal bank account, or any other bank account for that matter, on or before the due dates. However, the receipts from the four transfers named are to be paid into a separate account and, if the club do not pay the stage payments at the agreed dates, Ensco has access to this separate account ONLY, to take it's money. The very precise amounts and dates suggest that these are amounts that equal the amount due to Ensco, so it's therefore a form of insurance by Ensco that they get their money.
They CANNOT take any more than the agreed amounts and once the amounts are paid then the charge is cancelled. As far as I'm aware the three stage payments were made on the due dates, leaving the amount of £1m outstanding, which is why the charge has not been cancelled. Ensco are only due what they're due, they cannot hoover up all transfer money above this amount, although there is a caveat in the charge that says "any other contract of any other player"
In short (as I've typed far more than I intended) Eales does not get any more money if Leeds go up, Oxford United do. But he could have got the balance of his money sooner if they'd have gone up. But for all I know Erick, Anan and Horst could have agreed to pony up the last payment and it's about to be settled, meaning all future transfer money comes directly to the club anyway.