##05AB1E, 11 bytes##

/70/î'*T×s£

Explanation

/            # divide v by a
 70/         # divide by 70
    î        # round up, call this n
     '*T×    # push 10 asterisks
         s£  # take n up to 10 asterisk
             # implicitly print

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05AB1E, 11 bytes

/70/î'*T×s£

Explanation

/            # divide v by a
 70/         # divide by 70
    î        # round up, call this n
     '*T×    # push 10 asterisks
         s£  # take n up to 10 asterisk
             # implicitly print

Try it online

##05AB1E, 9 bytes##

/70/î'*s×

Explanation

/          # divide v by a
 70/       # divide result by 70
    î      # round up
     '*s×  # push that many asterisks
           # implicitly print

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##05AB1E, 11 bytes##

/70/î'*T×s£

Explanation

/            # divide v by a
 70/         # divide by 70
    î        # round up, call this n
     '*T×    # push 10 asterisks
         s£  # take n up to 10 asterisk
             # implicitly print

Try it online