On Scaling Decentralized Blockchains Paper: How is transaction/sec calculated?

I’m currently reading this paper on the scalability of Bitcoin and I’m struggling to understand some of the calculations.
On page 6 they calculate the 90% effective throughput, meaning the speed at which data can travel through the network if it needs to reach 90% of the network, is 55Kbps.
I don’t understand how they convert that to 26tx/s. As far as I understand 55Kbps / 0.25kb (throughput / transaction size) would be 220 tx/s and not 26 tx/s.
Can someone help my find my mistake?