Propositional variables connected by XOR will result in 1, if there are odd number of ones in the variables.
In the first case, there are 8 variables, resulting in $2^8$ combinations of 0s’ and 1s’ [eg. for 3 variables, $2^3$ sequence of combinations running from 000 to 111]. Out of which half of the combinations will have odd number of 1s’ which will be equal to $2^8/2=128$.
Similarly, in the second case, due to the conjuction operation, two variables should be 1 at the same time. Therefore, the total number of variables determining the result will be 4 (8/2). Hence, the combinations having odd number of 1s’ will be half of the total possible combinations. ie. $2^4/2 = 8$