140 miles is almost nothing.
70 miles will not harm the value of any car unless it is a very rare and valuable classic car that for some strange reason has never been driven since new so has "delivery miles" only on it (e.g. 7 miles)
If it is a nearly new car, it loses value the instant it is registered, as it then becomes a used car, no matter how many miles it has done. Other than that, it probably takes about 5,000 miles to make any difference to the value, and even then it will not make much difference.
If you are worried about the difference 70 miles will make to your car, you should not buy a car, as you will be worried about every journey.