Just don't fall into the trap that some others have of thinking that FnF's boards will be able to determine the amount/timing/form of capital raises. They only have the power to make suggestions; FHFA must approve anything FnF submit so it's FHFA that has the power here. All this capital rule says is that it will be FnF that starts the process.
The amount of a capital raise will be heavily influenced by the capital requirements FHFA sets, and HERA's definition of core capital restricts any capital raise to being some combination of new common shares and new non-cumulative preferred shares.
Timing is the only variable the boards have any real leeway on, and I'd imagine they would want to do this ASAP once the conditions are right.