That was actually a bad year, as that "free" $21 million represented a loss of about $30 million. $1.17 billion on Jan 1st 2016 is equivalent to $1.22 billion a year later due to inflation. So they would have had to generate $50 million just to break even in actual buying power terms.
No, they're saying that inflation that year was 4.3% ($1.22B / $1.17B¹) If you're only making 1.8% in investing it, you're not beating inflation, and your money, though nominally growing (number is going up), is decreasing in its real value (amount of stuff the money gets is going down).
(¹I think this is too high; BLS thinks inflation over 2016 was 2.5%. But their core point still stands: interest earned was below inflation.)
