Really simple question on Matrix rendering

Hi all,
I have a little problem with matrix rendering.
Here is a description of my report :
Landscape format (29.7cm by 21cm), report header and footer, one matrix
with 1 line group an 1 column group (easy ^o^)
Height of the matrix columns header : 1,3cm
Height of a line element : 2.3cm
Height of the report header : 1.7cm
Height of the report footer : 0.9cm
Margin (top and bottom) of the report : 0.5cm
So "Page height" - "Margins" - "Report Header" - "Report Footer" -
"Matrix Heder" = 16.1cm
And 16.1 = 7x2.3. So, if i'm right, there will be 7 rows by page
Here is the problem :
When I preview the report, I there are 8 rows instead of 7 on the first
page.
And what is really odd, the second page contains 7 rows, as
excpected...
I tried with a table instead of a matrix, just to see if I get the same
thing.
But with a table, I have 7 rows by page, on each page.
It seems that th matrix doesn'y use the same algorithm to calculate
pagebreaks than the table.
Can someone help me please ?
Thanks
DAOK,
Don't search it seems to be a bug of the preview.
When exporting to pdf, the report is correct.
If someone of the RS Team have some time to waste (^o^), I am
interrested in an explanation of the problem.
Thanks for reading ^O^
Bye