Q: How many times can the Plugornot Zero charge my iPhone or iPad?
A: This charger is a wall charger with a relatively small-capacity built-in battery. The battery is rated for 24.3 watt-hours. Due to some conversion loss, you can get about 78% of the stored energy out of the battery. 24.3 watt-hours x 0.8 gives 19 watt-hours.
In comparison, iPhone 8's battery is 6.96 watt-hours, and iPhone 7 has a larger battery of 7.45 watt-hours. While using your iPhone, the wall charger+battery combo should provide up to 2 full charges of your iPhone. If you're charging your phone while it's asleep or unused, you can get a little over 2 full charges.
The iPad (9.7") has a battery of 32.4 watt-hours. If you're using the iPad while charging it, the Plugornot Zero will charge your iPad up to around 50% before running out of juice.