Minor correction to normoblast population

The population size is the product of the production rate and lifespan.

vignettes/articles/model-description.Rmd

@@ -198,7 +198,7 @@ net_Ur <- sum(p$Ur_a_ss)
 | Symbol       | Description                           | Baseline value  |
 |--------------|---------------------------------------|-----------------|
 | \(\Uss\)     | RBC population                        | \(`r p$U_ss`\)  |
-| \(\gamma\)   | Normoblast population (bone marrow)   | \(`r net_n`\)   |
+| \(\gamma \cdot T_n\) | Normoblast population (bone marrow)   | \(`r net_n`\)   |
 | \(\rss(a)\)  | Reticulocyte population (bone marrow) | \(`r net_r`\)   |
 | \(\Rss(a)\)  | Reticulocyte population (circulation) | \(`r net_R`\)   |
 | \(\Nss(a)\)  | Normoblast population (circulation)   | \(`r net_N`\)   |