Found the answer to my own question.

Yes it is as i suspected. It is incremental. So if someone would like to get this value you should run:

declare @LazyPerSec bigint

SELECT @LazyPerSec = [cntr_value]

FROM sys.dm_os_performance_counters

where [counter_name]='Lazy writes/sec'

order by [counter_name]

WAITFOR DELAY '00:00:05'

SELECT ([cntr_value]-@LazyPerSec) / 5

FROM sys.dm_os_performance_counters

where [counter_name]='Lazy writes/sec'

order by [counter_name]