250 byte string: strange behavior

[admin]

What value exactly do you get in 32/1/4? Try adding log(value, x, y, z) before grp.write to check the variable contents.
Also getvalue() there is not needed since hours variable already contains the same value.

Code:

if hours ~= nil then
    grp.checkupdate('32/1/2', hours, 0.01)
else
  return
end

hour = math.floor(hours)
minutes = string.format('%02d', math.floor((hours % 1) * 60))
text = hour .. ':' .. minutes
grp.write('32/1/4', text)