Sorting error in “InfoPath Forms� folder

I have a field that displays salary in InfoPath form. When I try to display
and sort this field data in Outlook “InfoPath Forms� Folder, the sort is not
applied correctly. For example, when I sort them in ascending order, they
appear as follows: 1300 – 3000 – 3500 – 700; and when sorting them in
descending order, they appear as follows: 700 – 3500 – 3000 – 1300.

I tried all the kinds of number, currency, and decimal formats to set the
data type of this field in InfoPath. But that doesn’t work. Every time I have
a wrong sorting result in the “salary� column in Outlook.

Any suggestions please? It's urgent!

Are there any settings that I should modify first in Outlook?

Thanks in advance