Have I or Plua gone mad (math?)

I am really mystified - when running the test program below in
Plua2.0 both on my Palm Z22 and in Palmsim on my Windows PC I get the
results:

low1: 22.752188171 (it should be 18.457220875)
low2: 18.409012

I have no use for all the decimals but I find it worrying if Plua can
go that wrong?

It's generally a very nice program!

Regards
Morten

-- Calculation error.lua
low1=256*0.000777193+16*1.623011077-7.709917765
low2=256*0.000777   +16*1.62       -7.7099

print(low1)
print(low2)
gui.event()