Most antibiotics are bacteriostatic, meaning they inhibit the replication of bacteria. To achieve this effect you have to maintain a sufficient concentration of antibiotics over time. Taking double the recommended dosage would put you way over that concentration, but it wouldn’t achieve a greater inhibition on bacterial replication. As your body breaks down the substance, dosing with half the recommended frequency would put you below the minimal inhibitory concentration before your next dose, allowing some regrowth of the bacterial colony every day.