This forms works in conjunction with the 'Workspace Settings' form to help you map IntelliGantt or MS Project fields to existing SharePoint fields.
When you select a row from the Workspace Settings table and click 'Map Server Name', IntelliGantt uses the data type implied by the row selection (for example, Text1-Text30 imply a single line of text in SharePoint), queries SharePoint for additional fields with the same type and lists them. The current field, if available is selected for you, but you can change the selection to any available field.
IntelliGantt supports single line of text, number, integer, currency, datetime and yes/no (or boolean). Therefore, if you selected Number1-Number20 in the Workspace Settings form, this form would then show available fields typed as number or integer. If you selected Cost1-Cost10 in IntelliGantt, this form would then show available fields typed as currency. Same with datetime and yes/no.