The Studentized residuals are standardized. You said, "I tried specifying the alpha into 0.01 and it produced the same outputs" That statement is correct.
Your question appears to be related to detecting outliers. A studentized residual (SR) represents the residual in units of the standard deviation of the residuals. If |SR| > 3, then the residual is more than 3 SD away from the OLS line.
In terms of confidence intervals, the following is true:
If the data satisfy the assumption of OLS and the sample size is large, then the studentized residuals are approximately normally distributed. Therefore you would expect 95% of the studentized residuals to have abs values less than 1.96. You would expect 99% of the studentized residuals to have abs value less than 2.58. You would expect 99.9% of the studentized residuals to have abs value less than 3.
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