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The only digits which appear the same when reflected are $0$, $1$, $3$ and $8$, so we want to find the number of times the display on the clock is made up of these digits.

The first digit can be $0$ or $1$, the second digit can be $0$, $1$, $3$ or $8$, the third digit can be $0$, $1$ or $3$ and the fourth digit can be $0$, $1$, $3$ or $8$. Therefore there are $2\times 4\times 3\times 4=96$ different possible displays that are the same when reflected.
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.