Update User guide with methods accuracy & metrics time calculation

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.93%. Comparing base (2bbf89d) to head (91b5936). Report is 2 commits behind head on releases/1.1.0.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## releases/1.1.0 #76 +/- ## =============================================== Coverage 93.93% 93.93% =============================================== Files 28 28 Lines 1897 1897 =============================================== Hits 1782 1782 Misses 115 115 ``` | [Flag](https://app.codecov.io/gh/openvinotoolkit/openvino_xai/pull/76/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit) | Coverage Δ | | |---|---|---| | [dev-py310](https://app.codecov.io/gh/openvinotoolkit/openvino_xai/pull/76/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit) | `93.93% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.