This table makes no sense to me.
Under what circumstances would you calculate more than 12 ESFR heads to require a hose allowance more than 250gpm? When the * says you don't include those added due to obstructions.
For example, when you use them in control mode instead of in suppression mode. In those cases, you will need more water available in hose streams because it is expected that suppression will be achieved by fire firefighting. You could take a look at paragraph 126.96.36.199 and table 18.4 (d). The latter specifies some design requirements of more than 12 sprinklers.
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