seems fairly early on in a cycle for nitrite to go off the chart but maybe you're just one of the lucky few getting a very speedy cycle so never mind.
1 - you can just keep popping the 5ppm in every day (or whenever the ammonia drops down to 0) and wait for the nitrites to drop down to a level where you can measure them again
2 - you can just put 2/3ppm of ammonia in and this means you'll have less nitrite building up, it'll still be off the scale at first but it'll come back to a measurable level a bit quicker, then when ammonia and nitrite are both droppping to 0 in around 24hrs you ease back up to 5ppm of ammonia over a few days and then wait for it to drop in 12 hrs
3 - you can choose either to add 5ppm or 2/3ppm of ammonia but you start doing water changes to bring nitrite down to a measurable level every few days which makes it easier to meaure and makes sure that there's no nitrites inhibiting growth.
normally me and WD will say drop it down and do water changes, rabbut will say to leave well alone and don't do water changes.

that may not be the most helpful thing that we can't really agree but it's mostly because every cycle is different so we've all had our own experiences and had things work or not work for us and the people we've been working with.