The digits chosen must sum to a multiple of 3, but not to a multiple of 9. If no repeated digits are allowed, the combinations of digits that have the appropriate sums are

{1, 4, 7, 9}, {2, 4, 6, 9}, {2, 6, 7, 9}

These each can be arranged in 4!=24 ways, to give a total of 3*24 = 72 unique numbers with no repeated digits.

If digits are allowed to be repeated, there are 28 choices. When digits are repeated, the number of possible variations in the digit sequence is reduced. The choices are

{1, 1, 1, 9}, {1, 1, 2, 2}, {1, 1, 4, 6}, {1, 1, 4, 9}, {1, 1, 6, 7}, {1, 2, 2, 7},

{1, 2, 6, 6}, {1, 2, 9, 9}, {1, 4, 4, 6}, {1, 4, 7, 9}, {1, 6, 7, 7}, {1, 7, 7, 9},

{2, 2, 2, 6}, {2, 2, 2, 9}, {2, 2, 4, 4}, {2, 2, 4, 7}, {2, 4, 6, 9}, {2, 4, 9, 9},

{2, 6, 6, 7}, {2, 6, 7, 9}, {4, 4, 4, 9}, {4, 4, 6, 7}, {4, 4, 7, 9}, {4, 6, 7, 7},

{6, 6, 6, 6}, {6, 6, 9, 9}, {6, 9, 9, 9}, {7, 7, 7, 9}

Altogether, there are 295 different numbers that can be made with these sets of digits.

{1, 4, 7, 9}, {2, 4, 6, 9}, {2, 6, 7, 9}

These each can be arranged in 4!=24 ways, to give a total of 3*24 = 72 unique numbers with no repeated digits.

If digits are allowed to be repeated, there are 28 choices. When digits are repeated, the number of possible variations in the digit sequence is reduced. The choices are

{1, 1, 1, 9}, {1, 1, 2, 2}, {1, 1, 4, 6}, {1, 1, 4, 9}, {1, 1, 6, 7}, {1, 2, 2, 7},

{1, 2, 6, 6}, {1, 2, 9, 9}, {1, 4, 4, 6}, {1, 4, 7, 9}, {1, 6, 7, 7}, {1, 7, 7, 9},

{2, 2, 2, 6}, {2, 2, 2, 9}, {2, 2, 4, 4}, {2, 2, 4, 7}, {2, 4, 6, 9}, {2, 4, 9, 9},

{2, 6, 6, 7}, {2, 6, 7, 9}, {4, 4, 4, 9}, {4, 4, 6, 7}, {4, 4, 7, 9}, {4, 6, 7, 7},

{6, 6, 6, 6}, {6, 6, 9, 9}, {6, 9, 9, 9}, {7, 7, 7, 9}

Altogether, there are 295 different numbers that can be made with these sets of digits.