When a display case is set to "Emit at > 128", then it will properly emit a redstone signal when there are 129 items in the container. However, when it is set to "Emit at < 128", it will continue to emit a signal while X = 128.

I don't know if the issue here is that the behavior is incorrect, or that the tooltip is incorrect. But they do not match. The behavior is "less than or equal to" but the tooltip shows "<" (less than).

NeoForge 1.21.1
AN: 5.10.0

Repro (creative mode):

1. Fill a barrel with 128 oak logs
2. Place a display case
3. Set the case to monitor oak logs
4. Connect the barrel to the display case (wand)
5. Connect a redstone signal to the case
6. Set the display case to emit when oak logs are < 128

RESULT: The redstone is emitting
EXPECTED: The redstone would not emit, because there are not fewer than 128 logs in the barrel. Either that, or the tooltip would read "Emit at <= 128"

Note that adding 1 more log to the barrel turns off the signal.