To find the expected count you have to multiply the probability of the favorable event with the number of repetitions/rolls. For a fair dice, every number will have the same probability to occur. The dice have number 1 to 6 which mean there are 3 odd numbers (2, 4, 6) out of 6 possible number.
Then the probability for odd number will be: 3/6= 1/2
The expected count of odd numbers in 30 rolls will be= 1/2 * 30 =15 times.
