[DOCS] Refinement of microseconds information - 24.3 (#26224)

Added more detailed value to the microseconds description.

Extended info for #26134
Already included in
#26129

src/inference/dev_api/openvino/runtime/exec_model_info.hpp

@@ -44,7 +44,7 @@ static const char OUTPUT_PRECISIONS[] = "outputPrecisions";
 
 /**
  * @ingroup ov_dev_exec_model
- * @brief Used to get a value of execution time of the executable primitive, where Mcs = Microseconds.
+ * @brief Used to get a value of execution time of the executable primitive, where Mcs = microseconds (1μs=0.000001s).
  */
 static const char PERF_COUNTER[] = "execTimeMcs";