bug or missunderstood?

[Haplo]

Hello, if I run this program:

Code:

cls
dim a,b as ubyte
dim dw1,dw2 as uinteger
dim valor as uinteger
a=10
b=5
valor=a*b
print "valor:";valor
a=100
valor=a*b
print "valor:";valor
valor=10000
print "valor:";valor
print
valor=a*b
print "valor:";valor
print
dw1=10
dw2=5
valor=dw1*dw2
print "valor:";valor
dw1=100
valor=dw1*dw2
print "valor:";valor

the output in screen is:

valor:50
valor:244
valor:10000

valor:244

valor:50
valor:500

This is a bug?