First - theBase # is "223" This is the value in #Dec_temp

Then look at the math:
Testmath1 - (Dec_temp*(9/5)+32) = 255 -- this is wrong
PBP uses full precedence of math operators, and also uses braces to force out of order of calculation.
Secondly it also only works in integers.

As such (9/5) = 1.8 = 1 ( and is calculated first )
hence Dec_tempf = 223 * 1 +32 = 255

try ( Dec_temp*( 90 / 5 ) + 320 ) / 10
ie ( Dec_temp*18 + 320 ) / 10

Also, if you just leave it at ( Dec_temp*18 + 320 ) you can use simple math to get the basic temp and the first decimal.

Andrew