Does scanning with a Mac with Yosemite and Time Capsule take a long time?

[REDACTED]

I installed the free Avast for Mac because it has good reviews on CNET.  However, I must say that it is on 19 hours and still counting to do a complete scan on machine.  It is now  and  scanning my time capsule back-up and reads 200%.  A few questions I hope someone can help me with:
1.  Does it usually take this long?
2.  How do I know when its done?
3.  Put files in chest or delete?
4.  What are the files that say can't be scanned?

Any help will be greatly appreciated.

Thanks.

[Eddy]

1]
There is no way to tell how long a scan will take.
It depends on (but is not limited to)
- amount of files to be scanned
- speed of the system
- scan settings
- how many archives there are
- other processes running

2]
It will tell you when it has completed

3]
To chest.
If something is falsely detected, you can restore it from there.

4]
https://blog.avast.com/2014/02/28/how-do-i-handle-files-that-avast-cant-scan/