I think what would happen is that you can get a cancellation week. If you do this before the 30 day window (before April 25) I think you get the 59 day restriction on your cancellation week. If you wait less than 30 days (on or after April 25), you may be restricted to a 30 day reservation window. The cancellation week will be good for a year from the date of cancellation. you will have to pay a new fee when you do the exchange the cancellation week.
Alternatively, if you have an exchange in mind, you can retrade now (with payment of new exchange fee), but within the 59 days from May 25, 2019.