As noted by MacRumors, the offer is available in several countries, including the UK, Germany, Spain, Italy, South Korea, Japan, Taiwan, China, India, and France. The offer is not available in the United States.
In the UK, Apple is offering up to £50 of extra trade-in credit for specific iPhone and iPad models and up to £30 for certain Mac and Apple Watch models. Apple will automatically apply the additional trade-in credit during the process.
Exact trade-in values depend on the model of the device and other factors like its condition. Apple earlier this week reduced the base trade-in value of some devices. However, the offer, which runs until May 31, should reduce some of that loss for customers trading devices.