[tz] Precise meaning of AT 25:00

The Tokyo rule now includes the value 25:00 in the AT column. Can someone confirm the exact meaning of the 25:00? Is it a) an extended local time-of-day b) the actual duration from midnight at the start of day While similar, there would be a difference between the two definitions if there was a second DST gap/overlap earlier in the day. eg. imagine the case where DST starts at 13:00 (with a gap to 14:00) and ends at 26:00. With (a) the AT column would hold 26:00, while with (b) the AT column would hold 25:00 I'm pretty sure it is (a), but wanted to double check before it gets baked into APIs Stephen