RNG. Not an in depth answer but I believe is is at least partially dependent on sizeof base cell. Likely, yours will be 72 cell as it is common for grid tied. Off grid used to be more 60 cell, but seems 72 is becoming used more. Has to do with all those numbers on the data plate and how they add up when put in series. Combining either 2 or 3 panels is most common. This is somewhat determined by your Charge Controller and battery bank voltage.
Edit: just reread your post. Does seem quite large. I would expect you to have maybe 30 panels at most, likely less figuring 300w panels, likely arranged 3x10 or whatever. Most modern racking adds little if any to size. What panels are you getting?