For some odd reason i have seen and heard about appointment letters with salary reaching decimals (2 significant no.) as well... eg. DH 16797.91

It is the HR as well as Accounting policy that the salary is converted in to Dirhams from what ever the currency the parent company is using.

Accept the offer as it is or leave .... no negotiation... system generated figures...
Sounds wiered but they cannot change it...

but the extra allowance can be given to you apart from the figure in some other forms...eg. vouchers... redemtion of receipt you spend... furniture...

something like that but the figure will not be changed on appointment letter