Military units can be arranged in various formations. Here's an overview on how this may be implemented
If you table the number of units in the first row, in the second row and so on accordingly to the number of units in the group, you'll find a pattern in the units number intervals for a given row count: namely, the length of the first interval (0...6) is 6, the second (7...15) is 9 = 6+3 + 0, the third (16...28) is 13 = (6+3) + 3+1, the fourth (maybe) (29...46) is 18 = ((6+3) + 3+1 ) + 3+2.
The value of 46 is chosen by observing that the difference between the last value for a certain row count and the first value for the following row count is always 3; in this case, with 46 units 4 rows are formed: the first 3 with 12 units and the last with 10. For the next value, 47, we guess 5 rows with 10, 10, 10, 10, 7.