Meta Description Character Limit/Characters Being Stripped

When editing the Meta Tag Descripton field for products, Opencart is limiting the number of characters that I can place into the field. There is no rhyme or reason to the character limit. On one product the limit is 239, on another it's 251, and on yet another it's 243. I've tried editing from a couple different computers and from different browsers, so a problem with my machine can be ruled out. No matter how many characters I try to place into the field, i get the same result, once I click "Save" Opencart strips my description back to the previous character limit that it had in place.

Has anyone else out there came across this bug? Any help in resolving this matter would be greatly appreciated as tying up the SEO is the last step before we go live.

EDIT: We're using Opencart v1.5.5.1.

By default the limit is set to 255 characters. I don't know why it varies for you.
You can change the limit by going to myphp admin.
Go to the database, expand OC-Product_Description, expand Columns, select meta description or meta keyword and change the Length/Values

Where you able to figure it out?
I followed the instructions but could not find the option to increase values!

I was told this method is good for 2.0.2.0 but i still cannot find the option the change values. I looked in the myphptool, i opened up database and located oc_product_description but when i go in to i just see a chart with my products and their information. I cannot edit the digit limits, only the chart values, meaning change product name, price, etc.

probably simiar to this:
http://forum.opencart.com/viewtopic.php?f=190&t=148872
Ernie

google has again changed their character limit from 320 characters earlier few months back to normal mode of around 155 characters, you can check character tool for knowing the character limit of your title and meta description with/without spaces.

160 characters exactly.