Out of 100 population means about 95 of them will be in the range (8,12);

Since is within the range (8,12), then population mean is also 10 with 0,95 probability.

If we take 100 independent random samples from the same population and find confidence intervals for each of them, then about 5 of them will not cover the true population mean.

For every sample, that will give us sample mean equal to 10, will have (8,12) as the 95% confidence interval.