That too! It's pretty obvious that he's being taken advantage of by everyone he meets. If this was happening to some kindly grandpa in an old folks home, you'd call it elder abuse.
It was most obvious with the $10 trillion Ukraine minerals deal, which was nonsense cooked up by a senator to "sell" Trump on the merits of allying with Ukraine long-term.
Russia tried this approach too. Their offer is $12 trillion dollars -- of course it's more than what Ukraine supposedly had on the table -- a laughable amount considering their entire GDP is only $2 trillion! Even if they gave the USA something crazy like 10% of their gross domestic production (most of which is not exportable!) this would take 60 years of ruinous payments.
You can only throw a number like this at someone if you're absolutely certain that they're totally innumerate and won't laugh in your face.
Think about the second-order implications of this: multiple people in the Whitehouse or Congress are confident in their knowledge that Trump can't tell the difference between a billion and a trillion, and/or has no idea about the size of another country's economy.[1]
Just to clarify: This is not "my opinion" about his numeracy, or lack thereof! This is the opinion of multiple senior staff who have his ear.
[1] Think back to my point about Trump's world view being "dated" to the 1970s and 80s: Back then, Russia's GDP was on par with the United States -- they were roughly equal superpowers! That's where he gets his intuition from, his ballpark numbers, relative strength, etc... THAT is why he treats Putin as an equal instead of a tinpot dictator that just happens to have nukes.