diff --git a/src/libraries/DrawAccumulatorLib.sol b/src/libraries/DrawAccumulatorLib.sol
index 4f8ef4c..f422d89 100644
--- a/src/libraries/DrawAccumulatorLib.sol
+++ b/src/libraries/DrawAccumulatorLib.sol
@@ -161,56 +161,40 @@ library DrawAccumulatorLib {
       return 0;
     }
 
-    uint24 firstObservationDrawIdOccurringAtOrAfterStart;
-    if (_startDrawId <= oldestDrawId || ringBufferInfo.cardinality == 1) {
-      firstObservationDrawIdOccurringAtOrAfterStart = oldestDrawId;
-    } else {
-      // The start must be between newest and oldest
-      uint24 beforeOrAtDrawId;
-      // binary search
-      (
-        ,
-        beforeOrAtDrawId,
-        ,
-        firstObservationDrawIdOccurringAtOrAfterStart
-      ) = binarySearch(
-        _accumulator.drawRingBuffer,
-        uint16(oldestIndex),
-        uint16(newestIndex),
-        ringBufferInfo.cardinality,
-        _startDrawId
-      );
-      if (beforeOrAtDrawId == _startDrawId) {
-        firstObservationDrawIdOccurringAtOrAfterStart = _startDrawId;
+    // check if the start draw has an observation, otherwise search for the earliest observation after
+    Observation memory atOrAfterStart = _accumulator.observations[_startDrawId];
+    if (atOrAfterStart.available == 0 && atOrAfterStart.disbursed == 0) {
+      if (_startDrawId <= oldestDrawId || ringBufferInfo.cardinality == 1) {
+        atOrAfterStart = _accumulator.observations[oldestDrawId];
+      } else {
+        (, , , uint24 afterOrAtDrawId) = binarySearch(
+          _accumulator.drawRingBuffer,
+          oldestIndex,
+          newestIndex,
+          ringBufferInfo.cardinality,
+          _startDrawId
+        );
+        atOrAfterStart = _accumulator.observations[afterOrAtDrawId];
       }
     }
 
-    uint24 lastObservationDrawIdOccurringAtOrBeforeEnd;
-    if (_endDrawId >= newestDrawId || ringBufferInfo.cardinality == 1) {
-      // then it must be the end
-      lastObservationDrawIdOccurringAtOrBeforeEnd = newestDrawId;
-    } else {
-      uint24 afterOrAtDrawId;
-      (, lastObservationDrawIdOccurringAtOrBeforeEnd, ,afterOrAtDrawId) = binarySearch(
-        _accumulator.drawRingBuffer,
-        uint16(oldestIndex),
-        uint16(newestIndex),
-        ringBufferInfo.cardinality,
-        _endDrawId
-      );
-      if (afterOrAtDrawId == _endDrawId) {
-        lastObservationDrawIdOccurringAtOrBeforeEnd = _endDrawId;
+    // check if the end draw has an observation, otherwise search for the latest observation before
+    Observation memory atOrBeforeEnd = _accumulator.observations[_endDrawId];
+    if (atOrBeforeEnd.available == 0 && atOrBeforeEnd.disbursed == 0) {
+      if (_endDrawId >= newestDrawId || ringBufferInfo.cardinality == 1) {
+        atOrBeforeEnd = _accumulator.observations[newestDrawId];
+      } else {
+        (, uint24 beforeOrAtDrawId, , ) = binarySearch(
+          _accumulator.drawRingBuffer,
+          oldestIndex,
+          newestIndex,
+          ringBufferInfo.cardinality,
+          _endDrawId
+        );
+        atOrBeforeEnd = _accumulator.observations[beforeOrAtDrawId];
       }
     }
 
-    Observation memory atOrAfterStart = _accumulator.observations[
-      firstObservationDrawIdOccurringAtOrAfterStart
-    ];
-
-    Observation memory atOrBeforeEnd = _accumulator.observations[
-      lastObservationDrawIdOccurringAtOrBeforeEnd
-    ];
-
     return atOrBeforeEnd.available + atOrBeforeEnd.disbursed - atOrAfterStart.disbursed;
   }