אימות הזמנה נכשל עם הודעת שגיאה שאיני מבין

A non-staff user tried to invite someone via email. The invited person clicked on the link and tried to register themself. They filled out the form correctly, all input fields were confirmed with a green message. But below in a red box, following error message is displayed:

Validierung gescheitert: Max redemptions allowed sollte zwischen 2 und 10 sein.

(the mixture of languages is literally like this – the forum is in German). The message means translated to English something like:

Validation failed: Max redemption allowed should be between 2 and 10.

Neither the invited person, nor the inviting user, nor me do understand the error message. Can someone please explain what went wrong? (and maybe it’s worth to rephrase the error message?)

PS: Searching through the website settings, the search string max redemptions allowed did not lead to any hit. Searching only for max dedemptions I did find two hits (Invite link max redemptions limit=5000 and Invite link max redemptions limit users=10 which both are the default values. Discourse 3.6.0.beta1-dev ( 3352cec1bb )