Think about it this way:
What percentage of the time is it between 2 and 6? Here, we are asking for the percentage of time that it is greater than 2 and less than 6.
Now, 70% of the time it's greater than 2. Out of these outcomes, where we know it's greater than 2, only $2/7$'ths of them would be less than 6 (since there are now 7 possibilities and we want 3 of them). So, the chance of both greater than 2 and less than 6 is $(0.7)(3/7)=0.30$.
Your argument, where you multiply by .6, is incorrect because .6 is the chance that it's less than 6 in all cases. This is what I meant in my comment with "independence". You can find the probability of two events happening simultaneously by multiplying their respective probabilities if they do not influence each other's probabilities. If the two events do influence each other's probabilities (as they do here), then you have to use the so called multiplication rule: $ P(A\text { and }B)= P(A)\cdot P(A, \text{ given that }B \text { occurred}) $