diff --git a/modules/learn/pages/buckets-memory-and-storage/storage-engines.adoc b/modules/learn/pages/buckets-memory-and-storage/storage-engines.adoc
index 83e6dbd97f..790dc9afa2 100644
--- a/modules/learn/pages/buckets-memory-and-storage/storage-engines.adoc
+++ b/modules/learn/pages/buckets-memory-and-storage/storage-engines.adoc
@@ -53,7 +53,7 @@ For example, if a node is holding 5{nbsp}TB of data, Magma can be used with only
 | 100{nbsp}MB
 | [[quota-ref]]1{nbsp}GB<<quota-note, ^[1]^>>
 
-| Minimum memory to data ratio
+| Minimum memory to data ratio<<quota-note, ^[2]^>>
 | 10%
 | 1%
 
@@ -65,6 +65,12 @@ For example, if a node is holding 5{nbsp}TB of data, Magma can be used with only
 [horizontal]
 [[quota-note]]<<quota-ref, ^1^>>:: Magma's minimum memory requirement is higher at 1GB per node due to the more complex data structures it has to maintain.
 
+[horizontal]
+[[memory-note]]<<quota-ref, ^2^>>:: Memory refers to the memory allocated to the bucket.
+Disk space of the bucket refers to the data size of the bucket on the disk, including all of its replicas.
+This can be estimated by: (number of documents * average document size * number of replicas * expected compression ratio).
+On a running system, the metric `kv_logical_data_size_bytes` reflects the bucket's size on the disk.
+
 == When should you use Couchstore?
 
 The choice of Couchstore or Magma is set at the bucket level xref:manage:manage-buckets/create-bucket.adoc[when the bucket is created].