tone
The real tone here is sarcasm, expressing annoyance rather than genuine enthusiasm. Sarcasm works by saying the opposite of what's meant, relying on tone of voice, context, and shared understanding between speaker and listener to signal that "great" should be read as its ironic opposite rather than taken literally.
It isn't genuine joy, because nobody delighted about a new task would phrase it with the flat, deflated "Oh, great" construction — genuine enthusiasm sounds different in both wording and delivery. It also isn't simple surprise, since surprise wouldn't naturally pair with the word "another," which implies repetition and fatigue.
Sarcasm is notoriously hard for non-native speakers and even for text-based communication to catch, since it depends heavily on vocal inflection and shared context — this is part of why sarcasm often falls flat or gets misread entirely over text messages.
Quration — Quration English