the daughter nucleus left over from this type of decay is more positive than the parent nucleus.

 This type of decay is beta decay,

 When a beta decay occur a proton decays into a neutron, an electron and an electron neutrino

  The atomic number of the parent nucleus decreases by one, we know that an atomic number is the number of protons in the atoms of an element, this protons are positively charged.  

 Hence this is why in nuclear physics the  number of protons are not referred to as atomic number but are called nuclear charges,

Therefore the overall charge of the the atom decreases when a protons changes to a neutron.

 On the the other hand the daughter nucleus formed has more protons than the parent nuclei and hence the more nuclear charges,

See the example below

²³⁴ ₉₀Th → ²³⁴ ₉₁Ac + ⁰ _-1e

 The daughter nucleus is actinium-234 with nuclear charge of 91 while the  parent nucleus is torium-234 with  nuclear charge of 90,  the daughter nucleus has more charge than  the parent nucleus.