How to estimate Coverage and number of scanning ports

Hi,

Now I research how to scan quickly and effectively, and I try lowering
number of ports.
(I mean that I want more effective result with fewer ports).

According to the book "Nmap Network Scanning" by Fyodor, at p.141,
- 576 ports : 90% Effectivenss
- 1558 ports : 95% Effectiveness
I take "Effectiveness" as Coverage,
so when I scan 600 ports, I guess coverage is over 90%. I want to
estimate such number.

However, I think I need 2 benchmarks:
 One is remote scanning(over the internet) case,
 and the other is internal scanning(such as inside my office) case.

So I have 2 questions:
1) Are above number(Book "Nmap Network Scanning") estimated by remote
scanning? or internal scanning? or mixed?
2) Does anyone know such a document about "Scan coverage and number of ports"?

Thanks,
--
Osumi, Yusuke
[email protected]
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