I'm not an up to the minute expert so maybe this is the new normal, but in my experience, those ratios are usually more like 1:3 or 1:4. It's pretty normal for VC's to own 30-35% of the company after a Series A.
Very hot and high growth companies (Facebook, famously) have been able to sell off single digit percentages of the company with incredibly high valuation increases between rounds. But those results may not be typical.