Update attr documentation

Author: arsenm

llvm/docs/AMDGPUUsage.rst

@@ -1645,9 +1645,9 @@ The AMDGPU backend supports the following LLVM IR attributes.
                                              reduced by heuristics.
 
      "amdgpu-max-num-workgroups"="x,y,z"     Specify the maximum number of work groups for the kernel dispatch in the
-                                             X, Y, and Z dimensions. Generated by the ``amdgpu_max_num_work_groups``
-                                             CLANG attribute [CLANG-ATTR]_. Clang only emits this attribute when all
-                                             the three numbers are >= 1.
+                                             X, Y, and Z dimensions. Each number must be >= 1. Generated by the
+                                             ``amdgpu_max_num_work_groups`` CLANG attribute [CLANG-ATTR]_. Clang only
+                                             emits this attribute when all the three numbers are >= 1.
 
      "amdgpu-no-agpr"                        Indicates the function will not require allocating AGPRs. This is only
                                              relevant on subtargets with AGPRs. The behavior is undefined if a