The project files supplied for use with U-Tab are very likely to contain default bases.
These are defined by using the original routing instructions that were applied in your questionnaire design. U-Tab specification files contain this information so that when you select a question that was answered by a sub-set of the sample, your displayed table is automatically based to valid respondents only.
Default Base Indicators (to the left of the Base Area) change colour if the current table contains default bases. To find out their definitions, hover your mouse over the coloured indicator or look to the right of the status bar.
You are not able to change the default base definitions, but you can clear them to calculate percentages on a larger sample.
See also: Defining a new base