There is two major ways to set the cursor at a given position within a page, <R..> <C..> or <AT> tags.
In the sequence <R1><C5>, <R1> is the first printable row and <C5> the 5th printable column of the printer.
vpxPrint keeps track of the printers margins to shift the text or the image. The first printable row and column are not at the physical top of the paper but depends on the printers model. <R> and <C> tags provide different results with different printers.
It's usually not a problem.
<AT=10,10> sets the cursor at 10mm exactly from the top and 10mm from the left of the physical page.
The printers margins are subtracted from the value to set the cursors position.
The <AT> tag allows to write a text at an absolute position, independent of the printer. This is useful when you use preprinted forms, for example.
If the two types of positioning are mixed in a report within a page, the relative objects position changes with different printers.
Always use the same coding convention <R><C> or <AT> within a same report.