How thunderbolt 3 USB-C is able to provide 40 Gbit/s?

According to Thunderbolt site they claim that TB3 can provide speed Up To 40 Gbit/s !

But TB3 USB-C is configured with 4 PCIe lane designs which can provide only 32 Gbit/s ! (according to wikipedia)

So there is a bottleneck here !! TB3 USB-C should not be able to throughput more than 32 Gbit/s so how they are saying 40 Gbit/s !?
 
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