John Gill Commentary Numbers 20:15

"how our fathers went down into Egypt, and we dwelt in Egypt a long time; and the Egyptians dealt ill with us, and our fathers:" — Numbers 20:15 (ASV)

How our fathers went down into Egypt
Jacob and his twelve sons, with their children:

and we have dwelt in Egypt a long time ;
even the space of four hundred and thirty years, (Exodus 12:40Exodus 12:41)

and the Egyptians vexed us and our fathers ;
used them ill, brought them into bondage, and made their lives bitter, laid heavy tasks and burdens upon them, as well as slew their male children, see (Exodus 1:7–22) .