Confusion regarding Normal Distribution

GRE Quant Problem Solving
1

In the conceptual video on Normal distribution, Greg showed the rule as 68-98-100 as ETS ignores data far from 3 Standard Deviation.
There is a popular rule of 68-95-99.7
In the ETS Official Guide to GRE, it is said that Normal Distribution has a property saying that about two-thirds of the data are within 1 SD of the mean.
My questions are,

  1. For the within the 1 SD of the mean, what percentage of data should I count? 68% or 2/3?
  2. What percentage of data should be counted, while solving GRE problems, in 2SD range? 96 or 95?
2

Either should be OK; questions are unlikely to be concerned on whether it’s 96 or 95.
Also from my experience, most ETS questions in this area will give you the values.