Well ... reality and actual agreement looks different ... at first :
the AGNA did NOT count in 'numbers' but in tonnage only.
Fot what the germans were actually allowed in terms of sunbs ... read from wiki, the according 'chapter'of the text of this agreement :
In short :
they
were allowed 100 % of the commenwealth tonnage on subs. ... But for the moment agreed to restrain themself to 45 %.
A restaint to be reliefed by (simple) notice and some friendly discussion before welding the first plate.
And as it seem the Brits were prepared to accept this 100 % tonnage as something well within the abilities of the RN to deal with. Therefore it could be argued IMO, that if the germans start to (actually) build more subs in 1937/38, with the notification of not wanting to exceed ... lets say 70 or 75 %.
About the 'acceptance' of such a notification and rather low impact on british military ... 'countermeasures' :
- see not only above about the RN evaluation of sub-warfare in the interwar period (as of rather low importance)
- there is THE appeasement goverment atm ruling in Britain
I have no idea atm in how much subs of what type this might (be) tranlate(ed) into, but it would give the germans at least the possibility to ... prepare for even more to come.