“When it was evening,
He took his place
Reclining at the table
With the twelve disciples.”
Ὀψίας δὲ γενομένης ἀνέκειτο μετὰ τῶν δώδεκα μαθητῶν
This is similar to Mark, chapter 14:17, and Luke, chapter 22:14. When it was evening (Ὀψίας δὲ γενομένης), Jesus took his place reclining at the table (ἀνέκειτο) with the 12 disciples (μετὰ τῶν δώδεκα μαθητῶν). Jesus and his disciples reclined at the table, not really sitting upright.