Added missing documentation (#3275)

Co-authored-by: Jonathan Shimwell <[email protected]>
Co-authored-by: Paul Romano <[email protected]>

docs/source/io_formats/settings.rst

@@ -252,11 +252,29 @@ to false.
 
   *Default*: true
 
+--------------------------------
+``<max_lost_particles>`` Element
+--------------------------------
+
+This element indicates the maximum number of lost particles.
+
+  *Default*: 10
+
+------------------------------------
+``<rel_max_lost_particles>`` Element
+------------------------------------
+
+
+This element indicates the maximum number of lost particles, relative to the
+total number of particles.
+
+  *Default*: 1.0e-6
+
 -------------------------------------
 ``<max_particles_in_flight>`` Element
 -------------------------------------
 
-This element indicates the number of neutrons to run in flight concurrently
+This element indicates the number of particles to run in flight concurrently
 when using event-based parallelism. A higher value uses more memory, but
 may be more efficient computationally.