can not set up SIP PE200 speedo

hi!my story..i have a vespa px 200 98',with an early drop bar,which it only came with the top cover uncut,and it was only for PE i purchased the PE sip digital speedo.

i have a 100/90-10 raceman rear tyre and a 3.50/10 raceman front tyre.

i use the internal cable  and just as the instrunctions said,i measured the front tyre and its 1370mm!!i entered the mm in the adj 3 menu,as wel as the 0,75 gear ratio,for the px 98,MY etc...

the readings are not the correct ones,according with the scooterhelp gear ratio topic..i always have on the screen,10-15 klm les eg 4th speed 6000 rpms 87 klm,3rd 6400 68klm ..ive tried every possible set up,and non of it seems to have the correct readings..

can you please tel me how to set it up corectly?

thanks dimitris!