Of course it's bottom heavy, you'll never have the same number of LTs as O4-O6s. That never would make sense, seeing that the attrition of LTs is so high. If you retain say 35% of that number, you'll have around 172 LTs staying in. Sounds about right to me. There are only so many O6 billets for the Navy, so I'm sure they try to keep the number of O6s at a fairly even number. What you need are O6s to retire to let the O5s in, but why would they want to go anywhere. Privilege of pay/rank/status is fantastic for those guys. That being said, retiring at O5 (think you can go 26yrs as an O5) isn't too bad either.
One thing I know is that if you want to get promoted, you better be good as a paper dentist. Clinicians don't go anywhere in the military. You may go back to clinic when you pick up O6, but you better follow the career path to get there.
I'm not sure if you have some retired/retained O6s in there. That's a policy that needs to go.