Rob Deer bat hash marks Question

[Swoboda4]

I've noticed on my Rob Deer (Detroit)bat L/S C243 that along with his uniform number 28 on the but end,there is also 4 hash marks,below the number, made with the same marker. I've noticed on some baseball cards of his with a view of the bottom of the bat,the same markings:
28
l l l l

Any ideas why it was marked like that?

[ironmanfan]

most likely denotes that the bat is 34 oz

[Swoboda4]

thank you Ironmanfan

[tigerdale]

yes, for sure..34 ounces.