Worried, not a lot. But watch them.
The chick is not really resting between pip and zip. I know we say that a lot on this forum, but it is really working hard. To prepare for hatch, it has to absorb the yolk, dry up blood vessels it no longer needs, and go through who knows what other changes before it can safely venture into the world. Some do a lot of this between internal pip and external pip. These usually zip pretty quickly after external pip. Some do a lot of this after external pip. These are the ones that we worry about because they seem to take forever. Twelve hours between pip and zip is not that unusual. And a few even zip before they have completely finished all this. Many of those still make it.
This is what makes it so hard to know when to intervene. If you try to help too early, you can wind up killing the chick. But if you wait too long, the chick can die. And if you open the incubator to help one, you might shrink wrap another. It is not an easy decision.
I don't know what is going on with yours. Your lockdown humidity is lower than I use, but the same humidities do not work for all of us. If you have had experience and those humidities have worked for you in the past, probably keep at it. But if you don't have a lot of experience with this incubator, you might consider trying to raise the humidity. I use a straw through a vent hole and put water in it using a syringe. If you use warm water, around incubation temperature, the humidity will come up faster than using cold water. You don't want to use hot water. That might cause a temperature spike if you add much hot water. Those incubators do not shed extra heat real well.
Yours may be perfectly fine. I honestly don't know. My concern is, with that humidity, the chick might be stuck in the shell and unable to zip. Might be, not definitely is. What I look for is yellow foamy stuff coming out of the pip hole. If you see that, the chick is stuck and needs help soon. I usually do not help unless I see that yellow foam. Some make it and some don't.
I'm not trying to panic you or make you worry too much. I'm just trying to give you an idea on what might be going on and what to look for. It is a stressful time. Good luck.