I'm not familiar with the decimal type column because I have never used it. I know that for selecting items within a specific size like that you would add a comparison in the query.
For example, if I wanted to get every entry from a table where say a moderation warning percentage was between 40 and 60, I would use the following command:
mysql_query("SELECT * FROM `members` WHERE `mod_warning` > 40 AND `mod_warning` < 60"); //Everything BETWEEN 40 and 60
mysql_query("SELECT * FROM `members` WHERE `mod_warning`>=40 AND `mod_warning`<=60"); //Everything INCLUDING 40 and 60
Using quotes around the value you are searching for will depend on the type of data stored in the column (integers won't need them, strings will). Since you have decimals in your numbers, it's safe to say you would need the quotes no matter what.
I don't know for sure if this will work because I haven't used the decimal type before so run a test or two in the actual phpmyadmin (or whatever you may use) under the SQL tab and make sure the results are what you want.