The Jewish bible states that Arpachshad is the father of Shelah, whereas Luke states that Cainam/Kainam is the father of Shelah, perhaps Luke may have read from the book of Jubilees, which is as follows: Jubilees [Chapter 8]

1 In the twenty-ninth jubilee, in the first week, [1373 A.M.] in the beginning thereof Arpachshad took to himself a wife and her name was Rasu’eja, the daughter of Susan, the daughter of Elam, and she bare him a son in the third year in this week, [1375 A.M.] and he called his name Kainam. And the son grew, and his father taught him writing, and he went to seek for himself a place where he might seize for himself a city. And he found a writing which former (generations) had carved on the rock, and he read what was thereon, and he transcribed it and sinned owing to it; for it contained the teaching of the Watchers in accordance with which they used to observe the omens of the sun and moon and stars in all the signs of heaven. And he wrote it down and said nothing regarding it; for he was afraid to speak to Noah about it lest he should be angry with him on account of it. And in the thirtieth jubilee, [1429 A.M.] in the second week, in the first year thereof, he took to himself a wife, and her name was Melka, the daughter of Madai, the son of Japheth, and in the fourth year [1432 A.M.] he begat a son, and called his name Shelah; for he said: ’Truly I have been sent.’

This reveals that Kainam, the son Arpachshad was 57 when his son Shelah was born. If you were to attempt to discover how many years elapsed between Noah and the birth of Abraham, according to the Hebrew bible and the OT which is Jerome's translation of the Hebrew, which make no mention of Kainam the father of Shelah, you would be 57 years out.