diff --git a/primary.tf b/primary.tf
index 04f18036..6b1db87e 100644
--- a/primary.tf
+++ b/primary.tf
@@ -1,4 +1,7 @@
 resource "google_compute_instance" "primary" {
+  /* The number of primaries must be hard coded to 3 when Internal Production Mode
+  is selected. Currently, that mode does not support scaling. In other modes, the 
+  cluster can be scaled according the primary_count variable. */
   count        = "${var.install_type == "ipm" ? 3 : var.primary_count}"
   name         = "${var.prefix}-primary-${count.index}"
   machine_type = "${var.primary_machine_type}"