Suggested modifications for age-selectivity type 11 (#216)

* Suggested modifications for age-selectivity type 11 when working with age-specific selectivity of 1.0 for a range of ages.

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Co-authored-by: Ian Taylor <[email protected]>
Co-authored-by: Elizabeth Perl <[email protected]>

9control.tex

@@ -1821,7 +1821,11 @@ \subsubsection{Selectivity Pattern Details}
 	\end{itemize}
 
 \myparagraph{Pattern 11 (size or age) - Selectivity = 1.0 for range}
-Length- or age-selectivity can be set equal to 1.0 for a range of lengths or ages. If the selectivity is length-based the input parameters should match the population length bin number that will have selectivity = 1.0. A simple example how this works is as follows:
+Length- or age-selectivity can be set equal to 1.0 for a range of lengths or ages. Like other selectivity types, it is specified in terms of the population, not the data bins.
+
+For age-based selectivity, parameters p1 and p2 are set in terms of population age. For example, p1 = 0 and p2 = 4 would mean selectivity of 1.0 for age-0, age-1, age-2, age-3, and age-4 fish. These parameters must be less than or equal to the maximum age, not the maximum age bin. All ages before and after p1 and p2 have selectivity equal to 0.
+
+If the selectivity is length-based, the input parameters should match the population length bin \textbf{number} that will have selectivity = 1.0. A simple example how this works is as follows:
 
 \begin{longtable}{p{4cm} p{0.9cm} p{0.9cm} p{0.9cm} p{0.9cm} p{0.9cm} p{0.9cm} p{0.9cm} p{0.9cm}}
 	\hline	
@@ -1836,8 +1840,6 @@ \subsubsection{Selectivity Pattern Details}
 	\item All length bins before and after p1 and p2 will be set near zero (1e-010).
 \end{itemize}
 
-The age-selectivity approach follows that detailed above for length-selectivity but is more intuitive since parameter p1 and p2 is set in terms of population age. 
-
 \myparagraph{Pattern 14 (age) - Revise Age}
 Age-selectivity pattern 14 to allow selectivity-at-age to be the same as selectivity at the next younger age. When using this option, the range on each parameter should be approximately -5 to 9 to prevent the parameters from drifting into extreme values with nil gradient. The age-based selectivity is calculated as $a = 1$ to $a = Amax + 1$: