Update IFA/MMS shift docs

docs/source/models/intervention_models/mncnh_pregnancy/oral_iron_antenatal/oral_iron_antenatal.rst

@@ -434,10 +434,20 @@ The same instructions written in pseduocode in the Birthweight_ section can be f
     - Subpopulation
     - Shift
     - Note
+  * - None
+    - Overall baseline population
+    - Not covered by IFA at baseline
+    - -WEIGHTED_AVG_SHIFT * baseline_ifa_overall
+    - 
+  * - IFA
+    - Overall baseline population
+    - Non ANC attendees covered by IFA at baseline
+    - -WEIGHTED_AVG_SHIFT * baseline_ifa_overall + SHIFT_FALSE
+    - Hypothetical shift for calibration - only ANC attendees receive IFA
   * - IFA
-    - No supplementation
-    - Overall
-    - IFA_SHIFT
+    - Overall baseline population
+    - ANC attendees covered by IFA at baseline
+    - -WEIGHTED_AVG_SHIFT * baseline_ifa_overall + SHIFT_TRUE
     - 
   * - MMS
     - IFA
@@ -457,13 +467,23 @@ Where,
 
   * - Parameter
     - Value
-  * - IFA_SHIFT
-    - `Location-specific IFA_SHIFT values can be found here <https://github.com/ihmeuw/vivarium_gates_mncnh/blob/2bb721ab7b99ca60e284a0a3a948e6504d639a6d/src/vivarium_gates_mncnh/data/ifa_mms_gestation_shifts/ifa_ga_shifts.csv>`_
+  * - WEIGHTED_AVG_SHIFT
+    - SHIFT_TRUE * ANC1 + SHIFT_FALSE * (1 - ANC1)
+  * - SHIFT_TRUE
+    - IFA shift for ANC attendees.
+      `Location-specific IFA_SHIFT values can be found here <https://github.com/ihmeuw/vivarium_gates_mncnh/blob/2bb721ab7b99ca60e284a0a3a948e6504d639a6d/src/vivarium_gates_mncnh/data/ifa_mms_gestation_shifts/ifa_ga_shifts.csv>`_
+  * - SHIFT_FALSE
+    - IFA shift for non-ANC attendees.
+      `Location-specific IFA_SHIFT values can be found here <https://github.com/ihmeuw/vivarium_gates_mncnh/blob/2bb721ab7b99ca60e284a0a3a948e6504d639a6d/src/vivarium_gates_mncnh/data/ifa_mms_gestation_shifts/ifa_ga_shifts.csv>`_
   * - MMS_SHIFT_1
     - `Location-specific .csv files of MMS_SHIFT_1 values can be found here <https://github.com/ihmeuw/vivarium_gates_mncnh/blob/2bb721ab7b99ca60e284a0a3a948e6504d639a6d/src/vivarium_gates_mncnh/data/ifa_mms_gestation_shifts/updated_mms_shifts.csv>`_
   * - MMS_SHIFT_2
     - `Location-specific .csv files of MMS_SHIFT_2 values can be found here <https://github.com/ihmeuw/vivarium_gates_mncnh/blob/2bb721ab7b99ca60e284a0a3a948e6504d639a6d/src/vivarium_gates_mncnh/data/ifa_mms_gestation_shifts/updated_mms_shifts.csv>`_
 
+
+The IFA shifts above are relative to the overall baseline population-level GBD exposure values. Individually for each simulant we apply 
+the shifts to the exposure value sampled from GBD for that simulant. 
+
 .. todo:: 
 
   The values in these CSVs rely on the GBD 2021 LBWSG exposure distribution and ANC1 covariates and therefore will need to be updated when the GBD 2023 estimates are available.