Fix variable name for extra memory note

src/index.html

@@ -452,7 +452,7 @@
         <div class="note-box">
             <p class="note-box-title">📝 Note</p>
             <div class="note-box-content">
-                <p>Some libraries store grads in FP32, which would require an additional <d-math>m_{params\_fp32} = 4 * N</d-math> memory. This is done, for example, in Nanotron, because BF16 is lossy for smaller values and we always prioritize stability. See  <a href="https://github.com/microsoft/DeepSpeed/issues/1773">this DeepSpeed issue</a> for more information.</p>
+                <p>Some libraries store grads in FP32, which would require an additional <d-math>m_{grad\_fp32} = 4 * N</d-math> memory. This is done, for example, in Nanotron, because BF16 is lossy for smaller values and we always prioritize stability. See  <a href="https://github.com/microsoft/DeepSpeed/issues/1773">this DeepSpeed issue</a> for more information.</p>
             </div>
         </div>