Text-Element with unwanted margins by TCPDF

I'm struggling with some additional margins

$pageLayout = [
            $width,
            $height,
        ];
$pdf = new TCPDF('L, 'mm', $pageLayout, TRUE, 'UTF-8', FALSE);

$pdf->setCellPaddings(0,0,0,0);
$textBorder = array('LTRB' => array('width' => 0.001, 'cap' => 'butt', 'join' => 'miter', 'dash' => 0, 'color' => array(0, 0, 0)));
$pdf->Text($paddingLR, $paddingTB,$myText,0,false,true,$textBorder,0,'L',false,'',0,false,'A','C',true);

The border is only for visualisation.

Preview of rendered Text

now i'm surprised about the margins around the text. I'd expect, that the Text starts within the border line. The same for the space above the letters.

Does anyone have a suggestion how to make this work?