In Syntorial V2 the Unison Spread knob jumps between values 0 and 1. This is by design. However, in version 2.0.007 and earlier, there's a bug in which a few lessons expect you to set it to the middle 0.5 value. If you experience this, simply update to the latest version:

Mac/Windows

1. Log into your online account.
2. In the Syntorial section select “Downloads”
3. Download and install the latest version

iPad

1. Download the latest version from the App Store