TableForm[Table[NumberForm[CDF[NormalDistribution[],a+b]-0.5,{5,5}],{a,0,1,0.1},{b,0,0.1,0.01}],TableHeadings->{Table[NumberForm[#,{3,3}]&@a,{a,0,1,0.1}],Table[NumberForm[#,{3,3}]&@b,{b,0,0.1,0.01}]}]

P(X<0.15)=0.5+0.05962

0.5+0.05962

CDF[NormalDistribution[],0.15]

P(X<-0.15)=0.5-0.05962

0.5-0.05962

CDF[NormalDistribution[],-0.15]