Sample used in calculating the sample regression function Does the OLS (ordinary least squares) method of regression consider only one sample value in calculating the sample regression function (SRF)? If not, then how is the SRF created when there is more than one observation per $X_{i}$?
It is not very clear what you're asking, but if the model is of the form

$$
y_i = \beta_0 + \beta_1 x_i + \epsilon_i \tag{1}
$$

Then the sample regression function (SRF)

$$
\hat{y}_i = \beta_0 + \beta_1 x_i \tag{2}
$$

indeed only considers one value of $x_i$ at the time. If you have a situation in which several observations $y$ are associated with the same value $x_i$, then a linear model is perhaps not appropriate for describing your data