You may have a look at
this previous post
In your case a solution -even if not probably the best- can be:
1) Set a general quota n=300 for your survey
2) Create your 5 groups (G1, G2, G3, G4, G5) and a related duplicate set (G1b, G2b, G3b, G4b, G5b)
3) Use the following relevance equations for each group:
G1: ((substr(SAVEDID, -1) == "1") or (substr(SAVEDID, -1) == "2"))
G2: ((substr(SAVEDID, -1) == "3") or (substr(SAVEDID, -1) == "4"))
G3: ((substr(SAVEDID, -1) == "5") or (substr(SAVEDID, -1) == "6"))
G4: ((substr(SAVEDID, -1) == "7") or (substr(SAVEDID, -1) == "8"))
G5: ((substr(SAVEDID, -1) == "9") or (substr(SAVEDID, -1) == "0"))
G1b: ((substr(SAVEDID, -1) != "1") or (substr(SAVEDID, -1) != "2"))
G2b: ((substr(SAVEDID, -1) != "3") or (substr(SAVEDID, -1) != "4"))
G3b: ((substr(SAVEDID, -1) != "5") or (substr(SAVEDID, -1) != "6"))
G4b: ((substr(SAVEDID, -1) != "7") or (substr(SAVEDID, -1) != "8"))
G5b: ((substr(SAVEDID, -1) != "9") or (substr(SAVEDID, -1) != "0"))
4) Merge results for data analysis (G1+G1b … G5+G5b)
There is maybe a similar way using javascript, just moving (client side) G2, G3, G4 on G5 if necessary with no need to duplicate the groups… but I don't know if it's possible to retrieve {SAVEDID} value with js…