My PLE Counter value is 483.what is the safe side for PLE buffer manager value?
The Page Life Expectancy counter tells you for how many seconds an 8KB data page will remain in the buffer pool, before being flushed out.

A low number can be a sign of memory pressure, but it may also be a sign of nothing.

If your data access patterns involve a lot of report-style queries, reading a lot of data from large tables, this could be normal.

Monitor the value over several days, at different times in the day, and you may find that this is an outlier. I have a customer whose PLE goes to zero every time a certain large index is rebuilt, but it steadily increases after that.

My first sense is to review indexes, and see if a well-placed index can help with large reads. Another best practice is to avoid using SELECT * FROM table if you can help it.

You may need to increase the physical RAM in the server, but that shouldn't be your first reaction.

(Read more here about PLE and NUMA nodes: http://www.sqlskills.com/blogs/paul/page-life-expectancy-isnt-what-you-think/)