Hiya Corvus13,
Thanks for using the forums to get this issue with your Galaxy Tab A's WIFI speed looked into, I am sorry if it's been causing some confusion seen as your other devices show okay speed!
Devices have different capabilities in terms of the max amount of mbps, it all depends on their specifications.
I'll be honest, I'm not that knowledgeable in regards to tablet specs, but I believe the Tab A is capable of speeds over 100mbps.
I've taken a look at your in home WIFI and Hub specs on my side and can't see anything that would indicate an issue, plus seen as other devices get on just fine I am leaning towards the issue being with your Tab A itself.
Like Lordoftime79 suggested, is the device all up to date?
Thanks,
Megan_L