why i am having different data entries between output and input ?

input : q1=- (127*gn1*h^3)/1935360 - (6439*gn1*h^3*t)/31933440 - (gn1*h^3*t^4)/48 - (2*gn1*h^3*t^5)/15 - (61*gn1*h^3*t^6)/270 + (14*gn1*h^3*t^7)/27 + (172*gn1*h^3*t^8)/63 + (1408*gn1*h^3*t^10)/405 + (512*gn1*h^3*t^11)/495

when gn1=1 and h=1 output: q1 =(512*t^11)/495 + (1408*t^10)/405 + (172*t^8)/63 + (14*t^7)/27 - (61*t^6)/270 - (2*t^5)/15 - t^4/48 - (6439*t)/31933440 - 1210491328414927/18446744073709551616