OnlyOffice spreadsheet can't open corretly xls file (wrong easy formula )

I have one problem
I can’t open correctly a easy xls file
in the cell a4 there are this formula

If I try oper with onlyoffice
the cell A4 there are wrong formula

I try oper the similar file but with exstention xlsx
and onlyoffice open correctly

Can you inform me why?

Hello @Antonio

First of all, please let us know version of Desktop Editors that you are currently using and OS where it is used.
Additionally, please provide the document itself for analysis.

In general, please note that Desktop Editors are supporting OOXML format documents (DOCX, XLSX and PPTX) as native format. Older formats such as XLS are converted automatically to OOXML format when opened in our editors.