Why Matlab shows me a small number as a ratio of very high numbers?

Does anyone know why Matlab shows me a small number as a ratio of very high numbers? When I run the code below, for a start r-zG should be ~21, instead matlab gives me the number as:

x3(t)*(z + 38413220085465947/1759218604441600)^(1/2) where the ratio is indeed 21...

for i=1:length(A(1,:))

   x3=sym('x3(t)');
   x1=sym('x1(t)');

   x1_diff=diff(diff(x1,t),t);
    r=D_o-thickness;
    rc(1,i)=r;
    % severe simplifications made
    a=r-zG;
    fI1=symfun((x3*sqrt(z+r-zG)),[t z]);

Answer 1

[A Jenkins]

vpa()