5.0.7(775) 64b - wrong behavior when deleting selected text in columnar selection

Hi!
Considering such text
<tab >I<tab >34724986
E<tab>I<tab >34634012
<tab >III<tab>30478232

<tab> - is only 1 byte ascii, but shows as 4 spaces

I selected (with columnar selection) block before 7-digit numbers, want to delete it.
Press Shift-Del. And got such result:

724986
4634012
30478232

My thoughts: at first line PSPad have to delete 3 bytes(chars), at second - 4 bytes(chars), at third - 5 bytes(chars). But it consider largest length of line to construct rectange to delete - 3lines*5 characters - and deletes 5 chars from each line, which is not correct. You need to treat <tab> character not as a 1 byte char, but variable length char...

Regards, Vadim