Exposure% calculation

How is Exposure% calculated?
When I change Margin from 50 to 100(no margin), the exposure value is doubled even though the system is roughly the same number of bars in the market. And the Risk Adjusted Return % (which is very important value for me) is halved. Could someone explain it? Many thanks.

InitialEquity 10 000 10 000
AccountMargin 50 100
Exposure% 13% 26%
Annual Return 14% 14%
Risk Adjusted Return % 109% 53%
All trades 1752 1749

Exposure as all other stats is documented in detail in the manual:
http://www.amibroker.com/guide/h_report.html

Exposure is relative to portfolio buying power. If you changed buying power ( by changing account margin) while leaving position size unaffected you are changing exposure.

@Tomasz,
Is it possible the backtest report is displayed on the chart ?

Because I still have problem that my analysis results and chart output are still different even though I have followed this link :
[http://www.amibroker.com/kb/2015/01/28/why-analysis-results-and-chart-output-may-differ/]

Thank you.