fortinet mistake in IPv4 addressess.

I did not find a vendor having mistake-free documents. It is not a big issue, especially in background knowledge. It is a human work and exposed to such. I checked the capture here. The "255.255.255.128" is the wrong part. The next part is correct. You could send feedback directly to Fortinet.

yes the suffix and number of hosts is correct. The mask itself is wrong inside the red circle.

But there is plenty of subnetting tables on the net you can look at.

Or you could calculate the mask from the suffix yourself.

/nn just gives you the number of 1s in the mask if you write it in binary numbering system instead of decimal.

eg. /24 means 24 1s in binary:

255.255.255.0 decimal = 11111111.11111111.11111111.00000000 binary :)

3x8 bit = 24 so suffix is /24 :)

or /27 means 27 1s

so in binary that would be 11111111.11111111.11111111.11100000

decimal that is 255.255.255.(1x2^5+1x2^6+1x2^7) = 255.255.255.(128+64+32) = 255.255.255.224

Hey Umesh,

thank you for reporting it; I have forwarded your feedback to the documentation team.

This should hopefully be fixed shortly.

Yep, typos are quite frequent in the documentation. You don't really fall for them with experience. The ones causing problem are not typos but bad explanation/wording leading to misunderstanding. The ones you have to read twice-trice to really understand what the author meant. 

Another typo:

https://docs.fortinet.com/document/fortiweb/6.4.1/cli-reference/637527/server-policy-persistence-policy