diff --git a/doc/manual/getting_started_core.rst b/doc/manual/getting_started_core.rst
index f4d3c8300..66f0c1240 100644
--- a/doc/manual/getting_started_core.rst
+++ b/doc/manual/getting_started_core.rst
@@ -221,7 +221,7 @@ Try this: ::
             with self.core_dma.record("pulses"):
                 # all RTIO operations now go to the "pulses"
                 # DMA buffer, instead of being executed immediately.
-                for i in range(100):
+                for i in range(50):
                     self.ttl0.pulse(100*ns)
                     delay(100*ns)