The longer the gauge length, the bigger the total elongation, because more "weaker parts" of the steal sample are incorporated, which have a lower yield strength. Similarly, if you have longer specimen, the measured srength will decrease, due to the weakest point which will finally decide the strength of the sample. The longer the sample (or the gauge length, if you wish) the bigger the probability to find weaker and weaker parts in the rod, -as absolutly uniform overall strength along the whole product, be is hot rolled or cold drawn is impossible to attain.