'producer' refers to a company producing something.
'notes' refers to a (bond-like) financial instrument issued by a company (rather than a government) giving creditors interest for a period of time (the rate is fixed so it drops in value as interest rates rise and vice-versa).
We thus have a noun 'notes' with modifiers identifying the total value of the notes ($1.5B) the interest rate (4.875%) and the expiry date (April 2022).
Grammatically the "subject" is $1.5 billion, semantically the "actor" is the value of each note. These would be used in the singular, e.g. "has dropped". However, pragmatically we can also regard the notes (by metonymy+metaphor) as dropping (in value) and as a plurality (more than one) and thus use plural agreement, viz. "have dropped". This "perfect" tense with "have" would emphasize the change of state, whereas the simple past "dropped" just notes that is happened.
We thus have a clause (indirectly quoted sentence) saying effectively
"the company's notes have dropped 9.25 cents each" + info on which, when and how much.
The second half, introduced by a participle (-ing word) says who said this.
The source, introduced by "according to", is Trace (turns out not to be a person).
Trace is identified as the name of a system for reporting on bonds (and notes).
FIRA is identified as the owner/operator/originator of this system.