Does "a sales manager of Panasonic" mean that there are many sales managers at Panasonic?
The only real answer is: it's a little ambiguous. Probably "yes", but it's hard to know for sure.
This is because of the way indefinite and definite articles work in English.
It's very common to use a when we're talking about someone's profession, because we're just saying that they're an example of that profession. For example,
Samir is a nurse.
Joon is a musician.
If we say
Dmitri is the cook at the restaurant
that means there is only one cook, Dmitri.
But when we use "a" with something more specific (like "of Panasonic"), it's unclear. For example, if I said
Berndt is a lawyer in Mecklenburg
he might be the only lawyer in Mecklenburg, or he might be one of many. There is no way to know. When we read
Sun Jay, a sales manager of Panasonic
the best guess is that yes, there is more than one sales manager at Panasonic, because if there was only one sales manager, it would be clearer and more common to say
Sun Jay, the sales manager of Panasonic.