Well, the team only has 11 games remaining against the West, so that obviously works in their favor.
Let's assume a 4-7 record in those games.
That leaves 21 games against the East remaining, including 1 game against Miami and two games against Indiana, meaning only 3 of those games are virtually guaranteed losses.
The team would need to go 14-4 in all of the other games to meet your prediction, however.
The East is weak, but Detroit, Atlanta, Chicago, Toronto, and Brooklyn all play the Celtics twice more this year, and those teams are fighting for playoff position.
I'm going to give the team some credit and assume 8-10 in those 18 Eastern Conference games. All told, that's a 12-20 record over the remainder of the season, with a final win total of 29.