Why is my lenovo yoga c930-13ikb showing incorrect battery level?

First of all, don't panic. This usually happens to a brand new battery. You just need to recharge it to 100% and make sure it is fully charged, then everything would be fine. Once you are convinced the battery reached its end of life. you may get one brand new pack here: https://www.storebattery.co.nz/lenovo-yoga-c930-13ikb-7.68v-7820mah-laptop-battery-store-for-new-zealand-p-244652.html

One more thing, we recommend you to use Battery Saver today, it is a battery saving power mode specifically optimized for Microsoft Windows 10. When the battery falls below 20% (by default), the battery saver will turn on automatically limiting background application activities and push notifications. 

Turn this on manually by going to Settings > System > Battery saver and toggle the button from Off to On. 

Use the following steps to adjust when the Battery Saver mode should automatically turn on:

• In the Battery Saver menu, click Battery Saver settings.
• Check Turn battery saver on automatically if my battery falls below and then choose between 5 and 100 percent battery life.
• Select the desired option(s): Allow Push notifications or Lower screen brightness.
• Add an APP exception to Battery Saver mode (if needed). APPs that are excluded from Battery Saver mode will be able to run in the background and send push notifications at all times.

Source from https://support.lenovo.com/us/en/solutions/ht117144