I'm reading abour crawl rate and it seems very important.

I have attached my crawl stats from GWT.

Also, can somebody explain crawl rate settings in GWT. Currently is checked "Let Google determine my crawl rate (recommended)". In which case I need to increase speed and will it decrease a quality of indexing?

My current sitemap stats:
Total URLs: 3469
Indexed URLs: 2965

I'm reading abour crawl rate and it seems very important

It's not.

Crawl rate is basically the time Google waits between sending requests. I personally would let Google bot determine how fast it needs to go

But look again:

Total URLs: 3469
Indexed URLs: 2965

If I say Google to send requests often, will these 2 numbers be more equal?

I don't think that crawl rate is that important and in fact you can change rate of crawling your site!

You can change the crawl rate (the time used by Googlebot to crawl the site) for sites that are at the root level - for example, www.example.com and http://subdomain.example.com. You can't change the crawl rate for sites that are not at the root level - for example,

http://www.google.com/support/webmas...e&topic=&type=

If I say Google to send requests often, will these 2 numbers be more equal?

No.

How many pages on the site are behind forms? these will not be crawled.
How many pages on the site are excluded in robots.txt? these will not be crawled.
How many pages on the site are blocked by a robots meta? these will not be crawled.
How many pages on the site are in password protected folders? these will not be crawled.

Count the URLs that bots are blocked from and I would expect your apparent disparity is reduced somewhat.

You need to keep your crawl rate medium in each case.

i don't think that crawl rate is that much important.