diff --git a/plugins/constraints/src/main/kotlin/app/aaps/plugins/constraints/objectives/objectives/Objective2.kt b/plugins/constraints/src/main/kotlin/app/aaps/plugins/constraints/objectives/objectives/Objective2.kt
index d2a4cc9b11..b18ec6fa29 100644
--- a/plugins/constraints/src/main/kotlin/app/aaps/plugins/constraints/objectives/objectives/Objective2.kt
+++ b/plugins/constraints/src/main/kotlin/app/aaps/plugins/constraints/objectives/objectives/Objective2.kt
@@ -227,18 +227,21 @@ class Objective2(injector: HasAndroidInjector) : Objective(injector, "exam", R.s
                 .option(Option(R.string.cob_longer, true))
                 .option(Option(R.string.cob_shorter, false))
                 .option(Option(R.string.cob_no_effect, false))
+                .hint(Hint(R.string.cob_hint1))
         )
         tasks.add(
             ExamTask(this, R.string.cob_label, R.string.cob2_question, "cob2")
                 .option(Option(R.string.cob2_longer, false))
                 .option(Option(R.string.cob2_shorter, true))
                 .option(Option(R.string.cob2_no_effect, false))
+                .hint(Hint(R.string.cob_hint1))
         )
         tasks.add(
             ExamTask(this, R.string.cob_label, R.string.cob3_question, "cob3")
                 .option(Option(R.string.cob3_longer, false))
                 .option(Option(R.string.cob3_shorter, false))
                 .option(Option(R.string.cob3_no_effect, true))
+                .hint(Hint(R.string.cob_hint1))
                 .learned(Learned(R.string.objectives_exam_learned_cob))
         )
         tasks.add(
diff --git a/plugins/constraints/src/main/res/values/exam.xml b/plugins/constraints/src/main/res/values/exam.xml
index 562e1415f3..c7ed0eca12 100644
--- a/plugins/constraints/src/main/res/values/exam.xml
+++ b/plugins/constraints/src/main/res/values/exam.xml
@@ -148,6 +148,7 @@
     <string name="cob3_longer">Setting profile to 150% will make the calculated carb absorption time longer</string>
     <string name="cob3_shorter">Setting profile to 150% will make the calculated carb absorption time shorter</string>
     <string name="cob3_no_effect">Setting profile to 150% will not affect calculated carbs absorption</string>
+    <string name="cob_hint1">https://androidaps.readthedocs.io/en/latest/Usage/COB-calculation.html#how-does-aaps-calculate-the-cob-value</string>
     <string name="iob_value">IOB value is affected by issued temporary basals.</string>
     <string name="iob_hightemp">High temp basal will not be given when your blood sugar is below target.</string>
     <string name="iob_negiob">Negative IOB for a substantial period in the absence of exercise suggests your profile is too strong and less insulin is needed in your settings.</string>