Here is Owen's own summary, from a response to Baxter:
The freedom, then, of pardon hath not its foundation in any defect of the merit or satisfaction of Christ, but in three other things:-
(1.) The will of God freely appointing the satisfaction of Christ, John iii. 16; Rom. v. 8; 1 John iv. 9.
(2.) In a gracious acceptation of that decreed satisfaction in our steads; so many, no more.
(3.) In a free application of the death of Christ unto us. Remission, then, excludes not a full satisfaction by the solution of the very thing in the obligation, but only the solution or satisfaction of him to whom pardon and remission is granted.[from Of the Death of Christ, p446 in Works, Vol. 10]