Panchanga · करणम्
Karana — Half of a Tithi
Since each Tithi runs roughly 24 hours, it's split into two Karanas — 11 named types in total, seven that repeat through the month and four that occur only once.
Movable Karanas — repeat 8 times each month
Fixed Karanas — occur once per month
The 30 Tithis × 2 Karanas per Tithi = 60 Karana slots per month; the seven movable names cycle through 56 of those slots (8 times each), and the four fixed names cover the remaining 4, always in the same position at the month's start and end.
See Tithi for the lunar days these are drawn from.