Mishnayos Oholos Perek 14 Mishnah 2

זיז שעל גבי הפתח וכו' – here we are speaking where the opening is concealed. And because of this, we require that the projection will have an opening of a handbreadth. And this is implied in the Tosefta (see Tosefta Ohalot, Chapter 14, Halakha 9).

ושעל גבי החלון רום אצבעיים – that is to say, whether a window whose measure is a height of two fingerbreadths, such as the remnants of the light-hole (i.e., opening in the wall from the start – see Tractate Ohalot, Chapter 13, Mishnah 1) or whether its measurement is as large as the hole made with the [large carpenter’s] borer/drill, as for example, that makes the light-hole at the outset, the projection that on top of both of this is whatever the amount.

ורבי יוסי אומר מלואו (only if its height is of equal measure/of full capacity) – a window whose measure is a height of two fingerbreadths, its projection it’s measure is with two fingerbreadths. But a window whose measurement is as large as the hole made by a borer/drill, its projection we also estimate/assess to be as large as the hole made by a borer/drill. But the Halakha is not according to Rabbi Yossi.