my SRS spreadsheet logged 半数 as half but the math is not mathing

I’m at 650 hours of Anki Phase 3. My database has 半数 mapped strictly to 'half the number' (numerical 0.5 ratio). But in my daily 120-minute reading block, I saw it used where 半分 should be. If the data parameters for these two aren't 100% distinct, my SRS efficiency algorithm drops by 4%. Does 半数 actually require discrete countable items, or is my dictionary spreadsheet glitched?