update the NNI architecture figure (#2805)

docs/en_US/Overview.md

@@ -10,7 +10,7 @@ NNI (Neural Network Intelligence) is a toolkit to help users design and tune mac
 The figure below shows high-level architecture of NNI.
 
 <p align="center">
-<img src="https://user-images.githubusercontent.com/23273522/51816536-ed055580-2301-11e9-8ad8-605a79ee1b9a.png" alt="drawing" width="700"/>
+<img src="https://user-images.githubusercontent.com/16907603/92089316-94147200-ee00-11ea-9944-bf3c4544257f.png" alt="drawing" width="700"/>
 </p>
 
 ## Key Concepts
@@ -86,4 +86,4 @@ The auto-feature-engineering algorithms usually have a bunch of hyperparameters
 * [Examples](TrialExample/MnistExamples.md)
 * [Neural Architecture Search on NNI](NAS/Overview.md)
 * [Automatic model compression on NNI](Compressor/Overview.md)
-* [Automatic feature engineering on NNI](FeatureEngineering/Overview.md)
+* [Automatic feature engineering on NNI](FeatureEngineering/Overview.md)
\ No newline at end of file

docs/en_US/Tutorial/ExperimentConfig.md

@@ -573,7 +573,7 @@ Used to specify designated GPU devices for NNI, if it is set, only the specified
 
 #### maxTrialNumPerGpu
 
-Optional. Integer. Default: 99999.
+Optional. Integer. Default: 1.
 
 Used to specify the max concurrency trial number on a GPU device.