After you put your lenses in, it wouuldn't be 30% anymore. Let it settle at between 45-55% (recommended range) would be good enough. Anything lower may dry up the lubrication in the lenses and the rubber may crack and if it's too high, fungus may grow.
Every dry cabinet comes with a manual, right? Reading the manual takes less time than posting a question here and waiting for answers.
In short: recommended RH range for cameras and lenses is 45-55% (also, see your camera manual, there is a chapter about "Environmental Conditions").
Watch the RH reading for the next days, it will fluctuate and start at higher level. Reason is: the dry box must get dry at inside and your camera as well (especially if you put it in with strap on). Don't get nervous, just watch. If RH goes below 45% then adjust the box accordingly (again: see manual). After a couple of days the RH will stabilize, adjust when necessary and leave it there. Once you open the door of course RH will go up. That's normal cause you let in humid air from outside. Don't do anything, within a few hours everything's back to normal.
From my experience, best RH range is between 40%-60%. Anything lower would be too dry and may cause problems with lubricants and other coatings. Higher than 60% may be too damp and may cause fungus growth.
The display type is irrelevant. The main question is: is it calibrated or not? Secondly: does it matter if the hygrometer shows 5% more or less as to justify the purchase of a (more expensive) calibrated device?