Just got upgraded home fiber to 1Gbps - provider router gives me 750mps in home. Deco only 250mps although in theory it can go up to 800+. Any reason why this would happen?

Deco in router mode

Setup is [ Provider Router ] > Ethernet cable > [ DECO ]

Speed of 250mps is at 5GHz standing next to the Deco, of course it drops futher out

Any ideas on the setup?