I don't have the game in front of me right now so I can't recall the Imperial mission card's title but it's the one that lets you draw one probe droid card for every four Rebel units at their secret base (probe droid initiative?). This came up during our play session tonight and I couldn't remember reading anything about rounding of fractions in the game. In our game, the rebels had 6 units at the rebel base meaning the Empire should get 6/4 or 1.5 cards. Does that round up to two cards or is it truncated down to one card?

Round down. For every four. There's only one four in six, not two. If I say you can trade four quarters for a dollar, and you have six quarters, two of those quarters are ignored.

Just divide all rebel units on the base into groups of 4 and draw a card for each group that contain 4 units. Is the case of 6 rebels, that makes a group of 4 and a group of 2. You get a probe droid card for the 4 but not for the 2. No need to round up or down or play with fractions.

Just divide all rebel units on the base into groups of 4 and draw a card for each group that contain 4 units. Is the case of 6 rebels, that makes a group of 4 and a group of 2. You get a probe droid card for the 4 but not for the 2. No need to round up or down or play with fractions.

You're just describing what rounding down is. The concept is the same.